Tuesday, October 17, 2017

Mosses of Central Florida 32. Trematodon longicollis

Trematodon longicollis Michaux (Bruchiaceae) is a fast-growing moss that
colonizes bare soil, forming small clumps.  Stems are short, upright, and bear a few narrow, elongate leaves.  The massive midrib extends to the tip of the leaf.  Leaf cells in the narrow blade on either side of the midrib are irregularly squarish.

Trematodon longicollis appears on bare soil.  This colony appeared in a flower bed that had been turned over just a few weeks earlier.  Note the thick, tapering neck below the more swollen spore chamber.
The most distinctive feature of this moss is the thick, tapering neck below the spore chamber of the capsule.  The neck in this species occupies about 2/3 the length of the capsules, which are curved slightly to the side atop long stalks.
On either side of the massive midrib, one can see the irregular
cells of the blade, that range from squarish to triangular.
Trematodon longicollis occurs in the eastern U.S. as far west as Texas and
Oklahoma, and to Pennsylvania in the north.  In Florida, it has been collected spottily throughout the state.

Friday, October 13, 2017

Mosses of Central Florida 31. Ephemerum crassinervium

The tiny rosettes of Ephemerum crassinervium
appear scattered on a mass of green,
thread like stems (protonemata). Photo by Robert
A. Klips, Ohio Moss and Lichen Association.
Ephemerum crassinervium (Schwaegrichen) Hampe (Ephemeraceae) is a tiny moss that is often overlooked.  As the name implies, it is an ephemeral plant that pops up in disturbed soil along drying shorelines in the dry season, and occasionally on rotting logs.  The plants then disappear again as their habitat is flooded during the rainy season.

The tiny rosettes are only a few mm high, though the spreading leaves may be as much as 2.5 mm long.  Leaves are toothed in the upper 2/3 and papillose (with small, translucent bumps) at the tip.  The midribs are weak, sometimes not evident at the base.  Leaf cells are irregularly long-rectangular and lined up in vertical rows.

The spherical spore capsules are also tiny and
often overlooked. Photo by Robert A Klips,
Ohio Moss and Lichen Association.
The spore capsules, when they appear, are also barely noticeable, as they lack a stalk and remain nestled in the center of the rosette.  The spherical capsules do not open regularly like most other mosses, lacking the typical mouth, teeth, and lids, but eventually rupture irregularly.

Ephemerum crassinervium is found widely in eastern North America, west to Texas and Nebraska, north to Saskatchewan, Ontario and Quebec (but not known in Maine), with some reports from Oregon.  In Florida, it has been sparsely collected from the panhandle to Collier County.

Two additional species have been reported from Florida.  E. cohaerens has been even more sparsely collected throughout north Florida, but not yet in central Floirda.  It differs from E. crassinervium in the smoother cells of the leaf tip, and the leaf cells lined up in diagonal rows.

E. spinulosum has a similar distribution as C. crassinervium, with some in Hillsborough and Manatee counties; cells of the leaf tip are spiny as opposed to smooth or papillose.

Saturday, October 7, 2017

Mosses of Central Florida 30. Atrichum angustatum

For other mosses in this series, see the Table of Contents]

Atrichum angustatum (Bridel) Bruch & Schimper (Polytrichaceae) is a relative of the common Polytrichum commune, but shorter in stature and with distinctly wavy leaves.  The upright stems are 1-2 cm tall, and like other members of the family, have vertical, fin-like sheets of tissue arising from the nidrib. Typically numbering about 10, these lamellae are also wavy.  Polytrichum has up to 20, and these are straight, compact and occupy most of the leaf surface. leaf cells are roundish and bulging to papillose  (with short, hard, translucent bumps).

The upward-facing rosettes of narrow, wavy leaves resemble a tiny bromeliad. The lamellae can be seen along the midrib,  running the length of the leaf. All photos by Robert A. Klips, Ohio Moss and Lichen Association. 
The wavy sheets of tissue, or lamellae, can be seen arising from the midrib.
Atrichum angustatum occurs throughout eastern North America, as far west as Nebraska and Texas, and as far north as Newfoundland. It can be found typically on exposed soil along roads and trails, as well as on soil exposed by fallen trees. It is uncommon in Florida, with just a few specimens from the northern part of the state down to Manatee County. It has been found in our area on creek banks and Indian mounds.

This reproductive specimen, with its narrowly cylindrical
sporangia, was photographed in Ohio.
This species may be limited in its abundance, in part, because male and female reproductive organs are borne on separate plants, which must occur in close proximity in order to form spores.  Sporangia, when found, are upright and narrowly cylindrical.

Saturday, September 30, 2017

The nearly forgotten art of comparative plant anatomy 2. Palm Fruits

Palm fruits are mostly single-seeded drupes, brightly colored
to attract birds or other animals for dispersal.  The large, hard,
seeds either pass unharmed through the digestive system
or are dropped to the ground as the fleshy pericarp is eaten.
From my brief introduction in "Everything you wanted to know about plant cells but were afraid to ask," you know that sclerenchyma is a collection of cells types characterized by the possession of a thick, rigid, secondary wall.  In the first part of this current series, I showed how sclerenchyma, along with other cell types, contribute to the complex and highly useful material we call wood.

Palm fruits may seem like an odd place to look for sclerenchyma, but I discovered early in my career as a plant taxonomist specializing in palms, that not only are such cell types present, but they are also highly varied in type and arrangement.  They represent an excellent case study for the usefulness of comparative plant anatomy.

One of the functions of sclerenchyma in general is to protect plant tissues from vegetation-chomping animals, and fruits are one of the most vulnerable of plant organs.  Fruits, and the seeds within, fill up with valuable nutrients as they mature.  The seeds must obviously be protected until they can be dispersed and have a chance to produce the next generation.  Fruits, however, are often meant to be eaten as part of that dispersal, but not until the seeds are mature.  So unripe fruits must be protected until then, but must become palatable, sometimes quickly and dramatically, at maturity.

The first layer of defense for the large seed within a palm fruit is something called the locular epidermis.  This is actually the interior epidermis of the  carpel that surrounds the seed proper.  In this layer, the cells often elongate perpendicular to the fruit wall, become pillar-like, closely-packed sclereids as the fruit matures.  Similar layers of cells have independently evolved in the seed coats of legumes.

A well-developed locular epidermis is common among palms of the subtribe Areceae (the large, advanced group that includes the betel nut, Areca catechu), but is quite varied in thickness,  even within genera.  Where it is not present, other forms of sclerenchyma take its place.

Another type of sclerenchyma found in palm fruits consists of individual cells resembling grains of sand, called brachysclereids or stone cells.  Those found in palms are similar to the gritty patches of stone cells found just below the epidermis in pear fruits.  Stone cells may be scattered within parenchyma tissue, grouped in clusters, or found in continuous layers.

In a great many palm fruits, there are also many fibrous bundles, consisting of  narrow, thick-walled fiber cells. As is generally true in vascular plants, fibers occur mostly around strands of vascular tissue (xylem and phloem), as protection for those tissues.  When additional protective functions (as in palm fruits) or supportive functions (i.e. in wood or the fibrous stems of palms and bamboos) are present, the volume of fibrous tissue can become massive and far in excess of what is needed to protect the vascular tissues. 
The fruits of Rhopaloblase ceramica have a very thick locular epidermis (bottom layer), consisting of elongate, pillar-like sclereids, packed tightly together. Above that, are three tiers of massive fibrous bundles that form around vascular tissues. In a band below the outer epidermis, are scattered stone cells (brachysclerieds), stained a purplish red. The very dark tissues present contain tannins.

Often intermixed with the fibrous vascular bundles close to the seed is a tissue with the seemingly oxymoronic name of sclerified parenchyma.  This is a region that begins as normal parenchyma in the young fruit, but become "sclerified" (develop secondary walls) as the fruit reaches its full size. In some of my earlier papers, I referred to this as "sclerified ground tissue," but that was too vague, as there are other forms of sclerenchyma in the ground tissue. (Ground tissue refers to the tissue  that fills the interior of leaves, stems, roots, and fruits, and consists mostly of parenchyma.

In the most specialized of the bird-dispersed palm fruits, we can usually see three distinct zones:

Close to the seed, we find densely packed fibrous bundles, sclerified parenchyma, and often a thickened locular epidermis. These hard tissues are typically fused together into a solid endocarp, or pit, which  remains with the seed when the rest of the fruit is removed.  This helps prevent the crushing of the seed when the fruit is eaten, or its penetration by burrowing insects.

Below the outer epidermis, one can often see an exocarp, a layer of stone cells, cells filled with bitter tannins, and sometimes fibrous bundles that protect against insect penetration.  Stone cells, which occur individually or in small patches, are particularly advantageous in this outer fruit region because they can loosen and separate as the fruit expands.  This allows the fruit to swell as it ripens, becoming more succulent.

Between these outer and inner protective layers, is the larger expanse of tissue referred to as the mesocarp.  This middle region may also be filled with fibrous bundles (the fibrous outer husk of the coconut being an extreme example), but in many specialized fruits it has been cleared of hard tissues, and consists only of soft parenchyma, which can swell as the fruit ripens, becoming fleshy, tasty and nutritious.  Such fruits presumably provide the most food for birds that feed upon them, and so  have a selective advantage.

Such well-defined zones are particularly conspicuous in the Ptychosperma alliance, which I studied as a graduate student.  In this group of palms native to New Guinea, Australia and some Pacific islands, another extraordinary transformation has taken place: the evolution of two radically different kinds of fibrous bundles, one occupying the endocarp, the other occupying the exocarp.

In Heterospathe, "naked" bundles of vascular
tissue are at the bottom, close to the seed, while
bundles further out contain only fibers.
The starting point for this trend can be seen in some palms outside of the Ptychosperma alliance, such as the Rhopaloblaste illustrated above, in which only the inner vascular bundles have a significant amount of vascular tissue, while the outermost bundles have a token amount, if any, and consist mostly of fibers. In the Heterospathe illustrated to the left, fibrous bundles without any vascular tissue are scattered throughout the mesocarp.

In the short spurs of fibers
in Orania, bits of
vascular tissue (ladder-like
protoxylem element in center)
can be found, illustrating the
role procambia in forming
fibrous bundles.
As another example, in the genus Orania, there are short, brush-like bundles of fibers that arise perpendicular to naked vascular bundles. They appear at first to be purely fibrous, but occasionally one can find a trace of mature vascular tissue within them.  This suggests that all fibrous bundles begin with a strand of embryonic vascular tissue (a procambium) as the organizational stimulus, but in specialized bundles, vascular tissues may or may not mature.

In Veitchia, inner bundles contain small
strands of vascular tissue (white spots)
and thick fibrous sheaths. Bundles in the
outer half of the fruit are purely fibrous.
Legend applies to all the diagrams.

In Veitchia, the outer fibrous bundles
are elongate and parallel with the
surface, but can separate from one
another as the fruit expands.

In the least specialized members of the Ptychosperma alliance, such Veitchia and Normanbya, fibrous bundles have already been separated into two distinct groups, the inner bundles have at least some vascular tissue and form an interconnected network, while the outer bundles are devoid of vascular tissue altogether, and become disconnected from one another as the fruit expands.

In the remaining genera of the Ptychosperma alliance, the outer fibrous bundles have become quite short and clearly separate from one another.  They are confined to the exocarp and are mixed with the brachysclereids.  Variation on the arrangement of tissues, however, is significant, and can be used to identify the different genera.  Some examples are below, but so that this post won't get too long, I refer you to my original paper on the Ptychosperma alliance, for more details. Similar trends can be seen in the other alliances of the subtribe Areceae, also with distinctive arrangements in different genera, and papers on those can be accessed through my general list of publications.

In Ptychosperma and other advanced genera, inner
fruit tissues follow the distinctive grooves
of the seed. The outer fibrous bundles are small,
short, and perpendicular to the surface. 
In Ptychosperma, outer fibrous bundles are short
and perpendicular to the surface. Brachysclereids
fill in between them.

An isolated  outer fibrous bundle from
The large fruits of Ptychococcus have an
exceptionally thick, hard endocarp,
consisting of a thick locular epidermis, a
massive layer of sclerified parenchyma, and
a mantle of fibers formed from the fusion of
adjacent fibrous vascular bundles. Short
fibrous bundles also mingle with
brachysclereids in the exocarp.

The fruits of Brassiophoenix have an angular
endocarp, like that of Ptychococcus, but with
the fibrous vascular bundles embedded within
the sclerified parenchyma.

Thursday, September 21, 2017

Mosses of Central Florida 29. Plagiomnium cuspidatum

Plagiomnium cuspidatum
The upright stems with broad ovate leaves and nodding capsules of
Plagiomnium cuspidatum suggest a species of the Bryaceae until one
takes a closer look.
Photo by Robert A. Klips, Ohio Moss and Lichen Association
(Hedwig) T.J. Koponen (Mniaceae)forms mats on moist soil, on rotting logs, or at the bases of trees in moist habitats, and has two forms of leafy stems; creeping sterile stems, and upright fertile stems.  Our local material appears to be all sterile, however.

The most distinctive characteristic of this species is its ovate to diamond-shaped leaf with a prominent midrib and conspicuous, narrow, sharp teeth in the upper half.  The leaf base is broad and clasps the stem.  The leaf cells are roundish, with thick, translucent walls. The leaves are twisted when dry.  The nodding, cylindrical to ovate capsules arise on elongate stalks from erect leafy stems.

The leaf of Plagiomnium cuspidatum  resembles that of a Bryum, but with 
many long, narrow teeth along the edge in the upper half.
Photo courtesy the Western New Mexico University
Department of Natural Sciences and the Dale A. Zimmerman
Herbarium,, Plants of the Gila Wilderness.
The nodding capsules are a plump, ovate-
cylindrric. Photo by Robert A. Klips, Ohio 
Moss and Lichen Association
This species, often filed under the older name of Mnium cuspidatum, is widespread in North America, even reaching Alaska and Greenland, and in Florida it is found from the panhandle to Miami-Dade County. Two other species are found in the state: P. ciliare only in the panhandle, and P. floridanum throughout the northern half of the state.  In P. ciliare the marginal teeth typically extend down toward the base, rather than just the upper half, and these are usually blunt.  P. floridium is nearly  indistinguishable, but the leaves more elliptical and with less flaring leaf bases.

The prominent, narrow teeth arise from a thickened border of rigid cells.  To the inside, cells are small, rounded, and thick-walled.  Photo from Wikimedia Commons,  licensed by Creative Commons..
This upright, fertile stems of this species might also be confused with members of the Bryaceae, such as Bryum argenteum, or Rosulabryum capillare, which also have broad leaves with a strong costa and nodding capsules, but their leaves do not have prominent teeth and their cells are much larger and more elongate.

Monday, September 4, 2017

Mosses of Central Florida 28. Climacium americanum

Photo courtesy Robert A. Klips, Ohio Moss and Lichen Association.
Climacium americanum Bridel (Climaciaceae) is a distinctive moss with a "tree-like" shape, and often of a yellow-green color.  It has upright stems that branch out into a number of spreading, leafy branches. It occurs in our area in wet habitats, most often on decaying logs in cypress swamps, but elsewhere in damp soil along rivers or marshy depressions.

In Florida, this species is distributed from the northern counties southward to Manatee County, with some records from Broward and Monroe counties.  It also occurs widely northward in the eastern U.S. and Canada, the Rocky Mountains,  Pacific Northwest, and Alaska.

The leaf has a distinct midrib, which tapers out just short of the leaf tip, jagged teeth in the upper part, a broad, spreading base without inflated cells, and cells that are "worm-like" (elongate,  tapered, and slightly wavy). Between the leaves are many branching, thread-like appendages called paraphyllia.

The broad leaf base and tapered tip of the leaf of Climacium americanum 
give it a triangular shape. Photo courtesy Robert A. Klips, Ohio Moss and
Lichen Association/
The spore capsules are erect, symmetrical, and narrowly cylindrical.

Although it was collected a number of times in our local Hillsborough River Basin in the 1970's, I have yet to find living specimens myself.  So I am grateful to Bob Klips of the Ohio Moss and Lichen Association for the use of his photos.
The worm-like cells of Climacium can be seen in this photo from Wikimedia
Commons of C. dendroides (not in our area). 

Thursday, August 24, 2017

Mosses of Central Florida 27. Dicranella hilariana

Dicranella hilariana (Montagne) Mitten (Dicranaceae) is typically found on moist, clay banks, but appears to have adapted also to the disturbed slopes of phosphate mine pits and may be partially covered with sand.  From the related genus Dicranum, Dicranella species differ mainly in their smaller size, shorter leaves, and lack of inflated (alar) cells at the base of the leaf. Like the other genera in this family, the leaf has a massive midrib, and the cells are squarish to rectangular.
Leaves of Dicranella hilariana have a thick midrib and square
to rectangular cells.
From the two other species of Dicranella occurring in central Florida, D. hilariana differs  primarily in the shape of its capsules, which are erect, symmetrical, and smooth, and in the color of the capsule stalks, which are yellow but may become somewhat reddish as they age. In D. varia the capsules are asymmetrical, somewhat bent to the side, and borne on red stalks. In D. heteromalla, the stalks are yellowish, but the capsules are nodding and  conspicuously furrowed.  
Found in a phosphate pit in Hillsborough County, this specimen of  Dicranella hilariana is partially
buried in the sand.  Note the symmetrical, smooth capsules and yellowish to reddish capsule stalks.  Latina 42 (USF)

Monday, August 21, 2017

Mosses of Central Florida 26. Dicranum condensatum

Dicranum condensatum Hedwig (Dicranaceae) grows in sandy soil throughout Florida, sometimes forming deep cushions made up of long, mostly dead stems and leaves, with green tips. The leaves along the stem are of the same size and shape and are produced indefinitely, in contrast with the related species Campylopus surinamensis.  It does produce spores, but apparently only rarely in our area.
A well-established clump of Dicranum condensatum nearly 6 cm deep.
Only the leaves in the top centimeter or so were alive when this specimen
collected ( Lassiter 2077, USF)
Leaf cells of  D. condensatum are squarish-rectangular in the
upper part, and the margins of the leaf are toothed. 

Like all members of the family, the midrib (costa) of the leaf is massive, but not as broad as in Campylopus, occupying only 1/10 to 1/5 the width of the  leaf in the lower part. Leaves are mostly 3.5-4.5 mm long, and more or less curled or twisted at their tips when dry.  Cells are angular squarish near the tip, becoming more elongate toward the base, and distinctly larger and empty at the base (alar cells).

Leaves are twisted-curled when dry.
Two other species of Dicranum are found in Florida, but not as common or widespread.  D. scoparium is found in humus, rotting stumps, tree bases, and has short-sinuous leaf cells. D. flagellare, found only in north Florida, has specialized whip-like branches with short, scale-like leaves pressed to the stem that arise from the axils of ordinary leaves. The related Dicranella has much shorter leaves.  Ditrichum pallidum (Ditrichaceae) is sometimes confused with Dicranum. It grows in similar habitats, but typically has much longer leaves on shorter stems, resembling tiny clumps of grass.

Tuesday, August 15, 2017

Mosses of Central Florida 25. Campylopus surinamensis

Campylopus surinamensis Müller Hal. (Dicranaceae) is a hardy, desiccation-tolerant moss found in the dry, sandy soil of the Pine Flatwoods and dry roadsides.  Synonyms include C. donnelli and C. gracilicaulis.  From other members of its family, it is typically distinguished by the habit of producing shoots with two forms of leaves.  Along the lower parts of the shoot, the leaves are small, widely spaced and pressed against the stem. In the upper part of the shoot, leaves are longer, and crowded into a distinct tuft.  It apparently does not produce spores anywhere in North America, but reproduces asexually by means of small, hooked leaves produced in the axils of the main leaves.
As a colony of Campylopus surinamensis develops, some shoots form as short rosettes, but later shoots elevate their rosettes atop sparsely foliated stems. Photo of Essig 20090209-1 (USF)

The leaves are dominated by the massive midribs, that occupy about a third or more of the leaf width at the base, and nearly all of the leaf in the middle and upward into the prolonged tip.  Other members of the family have still massive, but narrower, midribs, occupying less than a third of the leaf width at the base.  The upper parts of the leaves are toothed along the margins. Leaf cells in the narrow blade region are squarish to irregular, becoming larger and more rectangular at the base. Leaves are somewhat curved but stiff when dry, not curled.
The leaves of Campylopus species are dominated by their massive midribs.

Tuesday, August 8, 2017

Families Matter

You probably remember from introductory biology course, that the official way of naming a species is the binomial ("two-name") system. Each species name is composed of the genus name and the specific epithet.   For example, Quercus alba is the name for the white oak.  Quercus is the genus, which contains a number of other species of oaks, and alba is the specific epithet that refers exclusively to this one species.

In almost all scientific communication and labeling practices, however, a third identification tag, the family name, is added - e.g. Quercus alba (Fagaceae). This greatly increases the utility and comprehensibility of the naming system.

The binomial system itself evolved from a fundamental human instinct to recognize categories of things, and specific types within those categories. Before Linnaeus established the formalized latin system that gave us Quercus alba, there were "white oaks, red oaks, etc. (and the equivalent in various other languages), just as there  were John Smith, William Smith, etc. Referring to just a "white" or "John," or "William," doesn't tell us much at all.

The  binomial gives some context to a name, and helps us interpret new information.  If someone describes a new species, Quercus antarctica (hypothetical) for example, we immediately know that it is another species of oak.  We can predict that it will be a woody tree or shrub with simple leaves, and that it produces acorns. The family name adds another layer of recognition and predictiveness.

Suppose, for example, someone comes into the room raving about the spectacular specimen of Trigonobalanus doichangensis she'd seen at a botanical garden in Singapore.  I myself would have stared blankly at her, having no idea what that gibberish stood for.  But then she tells me that Trigonobalanus is a genus in the family Fagaceae.  A big light bulb turns on in my head. Fagaceae is the family to which Quercus belongs, along with Castanea (chestnuts), Fagus (beeches), and several other genera. Suddenly I have an approximate idea of what this plant is.

The family name is therefore extremely valuable for recognizing, characterizing, identifying, labeling, storing, retrieving, and providing relationship context for plant specimens. Sometimes it is of more value than the genus name for providing a rough idea of what a plant is and where it fits in relationship to other plants, as in the Trigonobalanus example above. This requires, of course, some knowledge of plant families. Learning the characteristics of families is a routine part of studying plant taxonomy, but will also be highly useful to anyone with an interest in plants.  Even the use of common names like "the orchid family" or the "iris family," etc., will be helpful when communicating with a lay audience.

The taxonomic system is a hierarchy of taxonomic categories, or taxa. Genus and family are two levels of taxa.  Theoretically, we could also append the names of higher categories, like orders, classes, phyla, etc. You will find those in textbooks, but for everyday use, they would amount to information overload. We can refer casually to important higher categories, like angiosperms, gymnosperms, green algae, etc., without really worrying about their technical names or their rank (their level within the hierarchy).

In this botanical garden label, the binomial, Galium odoratum, is most prominent.  Much additional useful information is also included, but most importantly, the family name, Rubiaceae, is included, in this case at the top left.  Incidentally, purists will point out that the binomial, by convention should be italicized, but that is not always possible.  Often, the machines that make labels do not have an italic font capability.  In fact, the formatting tools for the host service under which this blog is created does not allow for italics in the title, as can be seen in my posts on moss genera.
Photo copyright Oxford University, fair use. 

Familly names for plants have been standardized with the "aceae" ending, which is attached to the name of the first named genus in the family  The Asteraceae (sunflowers, etc.) gets its name from the genus Aster.  So you'll know when you're seeing a family name.  Some older names were different, ending in "ae,"  and using a descriptive term instead of a genus name as the base.  The old name for the Asteraceae was the "Compositae," referring to the composite or compound nature of the flower heads.  You will still see these type of names in the older literature.  Some of the other common ones are "Palmae" (for Arecaceae), "Gramineae" (for Poaceae), "Leguminosae" (for Fabaceae), "Labiatae" (for Lamiaceae), "Crucferae" (for Brassicaceae) and "Umbelliferae" (for Apiaceae).

The point(s) of these remarks are several:

1. For botany instructors and students, learning the characteristics of the plant families that occur in your area, and using plant family names when labeling or referencing specimens, has a huge practical value.

2. When identifying plants, recognizing the family narrows down your search and allows you to skip over what is usually the most difficult part of a taxonomic key.

3. Referencing the plant family when writing or talking about plants puts them into a context of relationship.  The taxonomic system is not an arbitrary set of names, but reflects the natural evolutionary relationships among plants.

4. For practicing taxonomists, we need to keep in mind the practical value of maintaining a manageable number of stable families with meaningful, recognizable, distinguishing characteristics. That's not always easy, given the directive of modern phylogenetic taxonomy to reorganize plant diversity into strictly monophyletic taxa, which often requires splitting of old familiar families into smaller units, or lumping familiar families into larger families with more diverse characteristics.  

Thursday, July 20, 2017

Mosses of Central Florida 24. Anomodon minor

Anomodon minor has creeping  primary stems with short, scale-like leaves
and semi-erect branches with larger, tongue-shaped leaves. Photo from dried
herbarium specimen: Merner s.n. 15 June 1979 (USF)
Anomodon minor (Hedwig) Lindberg (Anomodontaceae) is a creeping moss occurring on bark at the bases of trees.  It is distributed widely in North America, extending south to Hillsborough and Polk Counties in central Florida. It has
Capsules of Anomodon minor are erect (unbent) and symmetrical.
Photo courtesy Robert A. Klips, Ohio Moss and Lichen Association.
two orders of leafy stems.  The primary stems creep horizontally along the substrate, and bear relatively short, scale-like leaves, while branch stems are semi-erect to spreading, with larger, tongue-shaped leaves. Branch leaves are broadly rounded at the tip with a short, hard point, have a distinct midrib, and the cells are small, roundish, and papillate (with hard, translucent bumps). When dry, the leaves fold against the stem. Capsules are erect and essentially symmetrical.  In habit and leaves, it somewhat resembles members of the Thuidiaceae, into which this genus is sometimes placed, but in that family, primary stem leaves are larger than the scale-like branch leaves, in both types of stems there are leaf-like paraphyllia between the true leaves, and capsules are asymmetric and bent to the side.

Within the Anomodontaceae, Anomodon is distinguished from the only other genus, Herpetineuron, by the shape and other features of the leaves. In Herpetineuron, leaves gradually taper to a point and the cells are smooth, without papillae.  Three other species of Anomodon occur in Florida.  A. tristis appears to form thinner mats, occurs higher up on tree trunks, and is found only in the northern part of the state. A. attenuatus forms denser mats, with more frequently branched stems that lay more-or-less flat, and taper at the ends with increasingly smaller leaves.  In A. rostratus, leaves are long and taper to a fine, hair-like point.
Leaves of Anomodon minor are elongate, tongue-shaped and with a rounded
tip with small hard point. Cells are tiny, roundish and equipped with papillae.
Lighter streak in the center is the midrib. 

Thursday, July 6, 2017

Mosses of Central Florida 23. Hygroamblystegium varium

Hygroamblystegium varium (Hedw.) Mönk.(Amblystegiaceae) is another moss frequently found in aquatic habitats in central Florida, along with Leptodictyum, Fontinalis, and species of Fissidens. Its leaves are shorter and spread more 3-dimensionally around the stem than those in Lepidodictyum, and the stems branch more frequently. Fontinalis is easily distinguished from these genera as its leaves lack a midrib altogether. The leaf cells in Fontinalis are also more elongate and curved, and the stalks of the sporangia (capsules) are extremely short.  Fissidens, of course, is easily recognized by the smaller secondary leaves attached at each node with the main leaves.  Like Amblystegium and Leptodictyum, which are in the same family, the capsules of Hygroamblystegium are erect, but slightly curved, and arise from short stems along the creeping main stems.
Compared to the related genus, Leptodictyum, the stems branch more frequently in Hygroamblystegium, and the leaves
are shorter, more scale-like, and distributed 3-dimensionally around the stem.  The capsule is upright, but slightly curved and asymmetric.  From a dried specimen, Wagner-Merner s.n., 17 May 1969 (USF).

Leaf cells of Hygroamblystegium are short-rectangular or sometimes
more elongate.
The family Amblystegiaceae is one of many moss families in taxonomic flux.  Even the treatment in Flora North America (FNA) is self-proclaimed to be tentative, with the treatment of genera and species still controversial and unsettled. Hygroamblystegium and Amblystegium, each containing only one recognixed species, are weakly separated, and sometimes combined into a single genus. The principal differences noted in FNA are that the leaves of Amblystegium are smaller than those of Hygroamblystegium and the midrib is weaker, and that the plants lack paraphyllia (extra leaf-like or thread-like appendages between leaves).  Amblystegium is also said to be always terrestrial, while Hygroamblystegium is often (but not always!) aquatic.  By this definition it appears that Amblystegium serpens is found only in north Florida, and reports from central Florida need to be investigated.

A lucky shot of the tip of the capsule of Hygroamblystegium varium.
In herbaria, Hygroamblystegium varium is more likely to be filed under Amblystegium, and it might be best to leave them there until the taxonomic dust settles. Some other species have been recognized, including Hygroamblystegium tenax, H. fluviatale, H. humile, H. trichopodium, and H. noterophilum, but it seems clear that these are all just variants of  the aptly named H. varium.

Friday, May 19, 2017

Mosses of Central Florida 22. Leptodictyum riparium

Leptodictyum riparium (Hedw.) Warnst. (Amblystegiaceae) is the most common aquatic moss in central Florida.  It is commonly found growing submerged on rocks along rivers, typically in thick mats, or exposed on rocks or tree bases close to water.  Other aquatic mosses include some forms of Hygroamblystegium varium, and two species of Fissidens, which are much less common.  Aquatic species of Sphagnum are confined to north Florida.  Amblystegium serpens may be in our area, but voucher specimens need to be verified.
Leptodictyum occurs in thick underwater mats. The stems are long, straight and sparsely branched.  The leaves are spread stiffly in one plane, even when dry.  From Franck 3314 (USF).

Leptodictyon is distinguished from other aquatic mosses by its long, straight, sparsely branched stems, with leaves extending stiffly from the sides of the stem (in more or less one plane). The leaves remain more or less stiff when dry, by may be somewhat rumpled.  It rarely produces sporophytes in our area.   Hygroamblystegium has shorter, more branched stems that tend to be more curved when dry, and shorter, more triangular leaves distributed uniformly around the stem.  It is also more often found with sporophytes.   Species of Fissidens are distinguished by their doubled leaves.
The leaves of Leptodictum have a distinct midrib, but which
does not quite reach the tip. From Franck 3314 (USF)

The leaves have a distinct midrib, and the leaf cells are generally elongate with thin, inconspicuous walls. Sporangia, when present, are somewhat curved and asymmetric, but none have been found among the specimens at USF.
The leaf cells are somewhat elongate and tapered at the ends,
but do not stand out sharply under the microscope. From
Lassiter et al 559 (USF)

Saturday, April 29, 2017

Mosses of Central Florida 21. Introduction to the genus Fissidens and F. pallidinervis

An image of Fissidens taxifolius illustrating the basic flattened shoot structure
 of the genus, with doubled leaf.  Image by Ralf Wagner.
According to Flora North America, twenty species of the genus Fissidens  occur in Florida.  By definition all members of this genus have a peculiar flattened leafy shoot with double leaves.  At each node or insertion point along the stem there is a full-sized leaf and a smaller leaf. The leaves are attached sideways to the stem, creating a flat, frond- or feather-like shoot. The leaves do, however, tend to curl when dry. At the bottom of this post is my effort at a simplified, short-cut key to the species.

As in most large moss genera, the individual species are distinguished by technical characters, mostly microscopic features of the foliage, and can only be definitively identified by experts.  However, there are some shortcuts that can help narrow down the choices in the relatively small number of species found in Florida (there are 450 species world-wide, 37 in North America), including the habit and length of the capsule stalks.

A dried specimen of Fissidens pallidinervis in the
herbarium at USF.  Note the relatively short stalks
of the capsules (sporangia), and the twisted  dry
Fissidens pallidinervis Mitten is relatively common in Florida, from the panhandle to the keys.  It is documented elsewhere only in Louisiana, but might be expected to show up in southern Georgia, Alabama, and Mississippi.  It typically occurs in moist areas at the bases of trees or on decaying logs, but found in our area also on shell mounds.

 From the other 19 species it is distinguished by a combination of  details, mostly of the leaves.  The cells of the leaf, on either side of the prominent midrib, are tiny, roundish and papillate, which means they bear small, translucent bumps on their surface.  This species has 2 or more such bumps, while some species have only one, and others have none (are completely smooth).

A single shoot from the specimen above.  Note that three
sporangia are rising from a single point on the stem.
The leaf cells of  Fissidens are small and roundish.  In this view,
the papillae can be detected as tiny bright spots of lighter
The shoots are tiny, about _mm long, and each may produce 2 or more sporangia near the shoot tip.  The stalks of the sporangia are relatively short, compared to other members of the genus, about 2 mm long. Only F. leptophyllus is in the same range, but in that species there is a clear limbidium ( a row of scleried-like cells) on the lower margin of the leaf, the leaf cells bear only 1 papilla, or are only rounded.  While others are variable, with stalks sometimes in this range, they are usually longer.

Provisional short-cut key to the species of Fissidens in Florida.

2_Sporangium stalks .5-.6mm………….F. fontanus
2_Sporangium stalks .7-1.5 mm……….F. hallianus
3_Sporangium stalks less than 6 mm long
        4_Occurring on bark, tree bases, not soil-specific
                   5_Sporangium stalks to 2 mm long
                         6_Leaf cells rounded or with one papilla; bases of trees, cypress swamps
                                                       …………………..............……..F. leptophyllus 
                         6_Leaf cells with several small papillae; bases of trees.....…F. pallidinervis 
                   5_Sporangium stalks 3.5-5 mm long
                        7_Leaf cells smooth to 1 papillate
                              8_Leaves up to 6 pairs, markedly toothed, cells 1-papillate; on bark,                                                                     logs, cypress trees…....F. serratus 
                           8_Leaves up to 25 pairs, not toothed, cells smooth to rounded; Bark, tree                                                             bases, rotten wood .................….F. santa-clarenis 
                              8_Leaves up to 10 pairs, minutely toothed, leaf cells smooth to bulging;                                                               bases of trees, soil............................…....... F. amoenus 
                      7_Leaf cells with several small papillae; leaf apex ending in a sharp, clear                                                               cell, on soil, banks, roadsides,  uprooted trees …….F. elegans
           4_Occurring on calcareous soil or rocks
                    9_ Found throughout Florida 
                            10_ occurring primarily at bases of trees; leaves in a pinnate pattern, up to 28 pairs
                                    ..........................................F. subbasilaris              
                            10_ on moist limestone in ravines; Leaves in a palmate pattern, up to 12 pairs .
                                    ......................................................F. zollingeri 
                    9_Found in north Florida only; on wet soil or rocks along streams, 
                            11_ Found in Florida panhandle *;soil, rocks and stones in shaded  ravines                                                               ………......................................................……..………..F. pellucidus 
                           11_Found in northern peninsular Florida, stems branched,........F. obtusifolius
                          11_Found in northern peninsular Florida*, stems unbranched …F. minutulus 
3_Sporangium stalks to 10-11 mm long
                            12_Capsules somewhat asymmetric, 1 mm long; occurring on bare, often clay, soil 
                                  .......................................................................................….. F. bushii 
                            12_Capsule 1.8 mm long; occurring at bases of trees, roots…......... F. dubius 
                            12_ Capsules symmetric; bases of trees, soil, logs .................…….F. bryoides 
3_Sporangium stalks to 15 mm long
                          13_ Capsules to 2.5 mm long, symmetric; on calcareous soil, north Florida only
                                                  ................................………………..F. polypodioides 
                          13_ Capsules to 1.5 mm long, asymmetric; seeps, moist rocks, soil;  central Florida
       3_Sporangium stalks to 25 mm; on seeps and rocks with dripping water……….. F. adianthoides 
       3_Sporangium stalks to 17 mm; on moist soil .humus, .rocks ................................…….. F. taxifolius 

*Questionable records of F. pellucidus and F. minutulus in Collier County, far removed from their north Florida ranges

Saturday, March 11, 2017

Mosses of Central Florida 20. Polytrichum commune

[For other mosses in this series, see the Table of Contents]

Polytrichum commune Hedwig (Polytrichaceae) is the giant among Florida mosses, with stems up to 10 cm. long. The stems are upright, with numerous stiff, narrow leaves.  It is not common in Central Florida, but when  found,  it is usually in extensive, dense colonies.
A colony of Polytrichum commune growing near Ft. Lonesome, Florida, in
Hillsborough County.  Many of the shoots in this picture bear clusters of sperm-producing antheridia at their tips. Photo by Steve Dickman.
There are seven species of Polytrichum found in North America, out of 70 worldwide.  P. commune is found throughout North America, Eurasia, New Zealand and Australia.  I recently found it in Taiwan.

The single specimen with sporangia at USF
shows the impressive dimensions of
Polytrichum commune. It comes from
northern Florida.
The leaves in the Polytrichaceae are unusual in consisting mostly of a massive midrib covered with vertical sheets of tissue arising from the upper surface.  This makes viewing the leaf anatomy more difficult, but the edges of the leaf in Polytrichum commune are lined with distinctive sharp teeth.  The bases of the leaves flare out into a broad sheath, and only here can one see the shapes of the cells.

 The upper surface of a Polytrichum leaf is covered with vertical,
blade-like sheets of tissue, here seen in cross section.
Photograph by Kristian Peters; Creative Commons
Attribution-Share Alike 3.0"
The midrib of Polytrichum commune is thick and fills the entire
blade.  Distinctive hard teeth line the edges.

The base of the leaf flares out into a thin
sheath, where the cells can be seen to be quite
narrow and elongate.

Evidently, Polytrichum commune rarely produces sporangia in Central Florida, as we have   We have o such specimens in the USF herbarium.  I can only speculate on the reasons for this.  In order for sporangia to form, sperm cells must swim from the tip of a stem where they are produced to the tip of a stem where eggs are being produced.  The large size of Polytrichum commune would make the conditions where this process could take place rather rare, particularly in the relatively hot and dry climate of Central Florida.  The species is at it's southern limit here. The one specimen with sporangia I've seen was collected in northern Florida.

 In addition, the colonies of Polytrichum are unisexual - they produce either sperm or egg, so two colonies of different sex must intermingle for sexual reproduction and spore-formation to take place.  The size of the plants would add to the difficulty of such mingling, and it is possible that some colonies in our area were established by a single spore, and hence unisexual.  In the photo  of living plants in Hillsborough County above, the colony appears to be all male.

Incidentally, in the process of researching this species, I found another excellent blog site for mosses from the University of British Columbia. Check it out for general information about the different groups of mosses.