Mosses of Central florida 46. The genus Leskea

Leskea gracilescens growing on the side of a tree.  Photo by
Robert A Klips

Three of the four species of  Leskea found in North America have been reported from Florida: Leskea australis Sharp,  L. gracilescens Hedwig, and L. obscura Hedwig.   These are creeping, irregularly branched, mat-forming mosses, often with a reddish coloration, found on the bases or lower trunks of hardwoods and cypress trees, or on decaying logs. 

A leaf of Leskea gracilescens, showing the small roundish
cells with papillae (translucent light spots).  Photo by Kalman
Strauss, posted in the Consortium of North American
Bryophyte Herbaria database.

Leaves are ovate and pointed, with midribs that usually end before the tip.  Leaf cells are small, roundish, and papillose, and the spore capsules are erect and more-or-less symmetrical.

Only Leskea australis is known from central Florida.  It has been found throughout the state, but has not been reported from the extreme south, the western panhandle or the Atlantic coastal counties. Elsewhere, it is found throughout the southeastern U.S.

A leafy shoot of Leskea gracilescens with an inset of the
papillose leaf cells.  Photo by Robert A.Klips

The erect, symmetrical spore capsules of Leskea gracilescens.
Photo by Kalman Strauss.

L. gracilescens and L. obscura are both widely distributed in eastern North America, live in the same habitats as L. australis, and differ in minor ways. L. grascilescens has been reported from several counties in North Florida, elsewhere throughout eastern North America, and L. obscura only from Leon County.

Our Leskea species are similar to Haplocladium microphyllum, also in the Leskeaceae, but in Haplocladium the spore capsules are bent distincly to the side, and the leaf tips more drawn out into a narrow point.  H. microphyllum is also more likely found in soil, rocks or damp wood than on tree trunks. 

Pond edges, liverworts, and the earliest land plants

.The edge of a drying pond would hardly seem like a hospitable place for plant life.  During the wet season it is submerged, and during the dry season it can be completely dried out.  Yet for the few months when the shoreline is retreating, during winter and spring in Florida, the sandy soil between high and low water marks remains moist, and supports a variety of small, but quick-growing plants that complete their life cycles before being inundated again.

Some green plants can be seen along this drying pond edge, but
the most interesting residents can only be seen close-up.

I have previously reported on some ephemeral inhabitants of such pond edges, including the sundew, Drosera capillaris, and several mosses, including Rosulabryum capillare,  Physcomitrium collenchymum, and some species of Micromitrium.  I expect to report on several other mosses with similar habits in the coming months.
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Recently, I was out walking in my neighborhood, and decided to revisit the same pond edge where I had collected Physcomitrium collenchymum in late March a couple of years ago. Now, in late January, I was quite surprised to find two completely different bryophytes,  Riccia cavernosa, and a species of Sphaerocarpos - both liverworts - but no sign of the Physcomitrium.  I shall have to pay attention over the next several months, to see if there is a succession of different species that might include later appearances of a  moss or two.

Riccia forms a flat, forking thallus, while Sphaerocarpos takes the form of a rounded mound of upright shoots.

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Riccia cavernosa is a thallose liverwort, meaning its body is in the form of a flattened, forking ribbon. Riccia species tend to spread outward from a central point, forming a round disk, at least when young, One can see here that the thallus is heavily pitted, giving it a spongy texture.

Sphaerocarpos species form cushions of odd egg-shaped shoots.

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.Finding these liverworts got me to thinking again about the very first land plants, which  most likely lived in a similar habitat, and were similar in growth forms to modern thallose liverwort like Riccia.  Phylogenetic studies indicate that the closest living relatives of land plants are in the green algal genus Coleochaete, which has a similar flat, disk-like growth form.  So it is easy to see an ancient transition from one to the other.

The green alga, Coleochaete, grows as
a flat sheet of tissue (A,B) that expands
outward from its center. The roundish
bodies are zygotes, that will eventually
undergo meiosis to produce zoospores (C).
from Essig 2015, after Haupt.

To be sure, some major adaptive innovations took place as green algae moved onto land, especially in their mode of reproduction. Coleochaete, like other green algae, produces zoospores through meiosis of the zygote, while all bryophytes have a diploid sporophyte generation that produces non-motile, dessication-resistant spores through meiosis of cells within a spore chamber or capsule.

[several interesting copyrighted photos of Coleochaete species can be seen at The Vine Tendril , and The Algal Web.

Also to be sure, Riccia is a modern liverwort genus, and I don't suggest that the first land plant were members of that genus that have been sitting around unchanged for 400 million years.  Most likely the ancestors of Riccia readapted to this habitat, as many others have over the ages, including the Sphaerocarpos, various mosses, and certainly the Drosera.

Part of that readaptation, is a shift back to the means of spore dispersal most likely practiced by the first land plants. In most bryophytes, the spore capsule is elevated by a stalk to facilitate wind-dispersal. The spore chamber of Riccia  is however very simple and lacks a stalk. It remains embedded within the thallus until the latter disintegrates, and the spores are then dispersed by water currents as the pond level rises, or on the feet of birds walking around in the mud.  Seeds of Drosera capillaris are probably dispersed in a similar way.

The sporophyte of Riccia is embedded within the gametophyte
thallus.  It consists of a thin wall (the capsule) containing a mass
of diploid tissue, which here has been transformed through
meiotic division into a number of hard-walled spores. From
Essig 2015, after Brown.

So the water-edge habitat has continued to host a dynamic community of ephemeral plants of similar growth form and reproductive habits since the very first colonization of the land.

Reference:
Essig, Frederick B., 2015. Plant Life - a Brief History. Oxford University Press.

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Flowers, Compound Flowers, and Superflowers

In the simple inflorescences of Indigo
(Indigofera spp., Fabaceae) new flowers
are produced at the tip for an extended
period of time, opening first at base, and
lasting only for a day or two.  Many
inflorescences with more complex
branching patterns still open just a few
flowers at a time.

An inflorescence can be defined as an aggregation of flowers on a specialized shoot that lacks ordinary leaves.  The lack of full-sized, photosynthetic leaves is the key to defining an inflorescence, as opposed to a series of single flowers along a leafy branch.  Within an inflorescence, leaves may in fact be present, but they are either smaller than normal, specialized in shape, conspicuously colored, or all of the above.

One common type of inflorescence, is one in which flowers open up one or a few at a time, for an extended period.  Examples include lupines, snapdragons, gladioli, and foxgloves.  Such inflorescences are adapted to induce "repeat visitors" - insects, birds, or other animals that remember the location of the plants and drop by each day to collect nectar or pollen from freshly opened flowers. This is a behavior known as trap lining.


In such flowers, a common means of avoiding self-pollination, is for the stamens and pistil within each flower to mature on different days. For example, pistils may be active and receptive to pollen on the day the flower opens, with the anthers opening to shed pollen 24 hours later. The common Amaryllis follows this pattern.

A common means of avoiding self-fertilization within individual flowers is to have pollen shed on one day (left) and stigmas receptive on another day (right).  This effectively makes the flowers male on one day, and female on another day.  

Compound, or false flowers, such as those of the sunflower family or the spectacular poinsettias, are actually condensed inflorescences adapted to look like a single large flower to pollinators, but still opening their flowers a few at a time to attract trap-lining animals.

In the compound flower heads of the Sunflower
Family, such as this Ice Daisy, the tiny flowers
(visible as the yellow rod-like structures)
around the outside of the central disk open first,
to be followed by flowers progressively closer
to the center.

In other inflorescences, the flowers mature all at once to create a single, massive pollination event.  I like to call these "superflowers." Super flowers don't necessarily look like a single flower, but they behave like one.  In the most specialized of these kinds of inflorescences, flowers are unisexual, and the opening of the male and female flowers is offset, such that the entire inflorescence behaves as a single, short-lived flower. Examples of these are found most spectacularly in the Aroid and Palm Families.

The Titan Arum, Amorphophallus titanum,
blooming at the U.S. Botanical Garden in
Washington, D.C., posted on Wikipedia.

The Titan Arum, which makes the news whenever it blooms in a botanical garden, produces a gigantic inflorescence in which all the tiny flower buds are mature when the large bract, or spathe, opens to reveal them.  They follow a similar strategy as the amaryllis flowers above, with separate female and male phases.  In this case, all the female flowers are active first, followed by the male flowers in a day or two.  This avoids self-pollination, as insects arrive during the female phase, bearing pollen from another inflorescence.  They then leave during the male phase, freshly dusted with new pollen.

Unlike the simple inflorescences
mentioned at the beginning of this post,
palm inflorescences complete most of
their development within their large,
protective bracts.  No new branches or
flowers will form after the bracts open. In
many, such as this Rhopaloblaste, the
flowers will continue to expand for a
while, and may open over a prolonged
period of time in order to attract trap-
lining insects. 

The inflorescences of palms, despite being rather large, appear to be fairly simple assemblages of small flowers, yet some of them behave in much the same way as the Titan Arum.  I made my discovery of these palm "superflowers" as a graduate student, first in Costa Rica, and later in New Guinea.

After waiting for a few hours at the edge of a swamp in Costa Rica, I found that inflorescences of a species of Bactris opened abruptly at dusk, displaying unopened male flowers and active female flowers nestled within them. The inflorescence emitted a musky odor, which attracted a variety of small flies, bees, and beetles. The male flowers opened to release their pollen 24 hours later. I observed the same thing in another species of Bactris later.

A year later, I was in Papua New Guinea and observed a nearly identical process in a species of Hydriastele.  I was able to get more detailed pictures of male and female flowers, along with their insect visitors, which I share below.

Though it consists of a number of branches, the inflorescences
of Bactris guineensis behave the same as that of the Titan Arum. Female
flowers, hidden among the larger male flowers, are
receptive to pollen soon after the large, fibrous bract opens.

When the bract of a Hydriastele microspadix inflorescence splits
open, the flowers are all mature, and arranged in triads of
two large male flowers with a tiny female flower between them.  

   

When the flowers are first exposed, the stigmas of the tiny female flowers, seen at the left between pairs of male flowers, are exposed, sticky, and receptive to pollen..  The male flowers (right) only open 24 hours later to release their pollen.  During the female phase, tiny flies and weevils are already present, attracted by the scent of the unopened male flowers.

One further example from the palm family comes from the mangrove palm, Nypa fruiticans, which lives in brackish water around river deltas and estuaries throughout the old world tropics. I spent a day observing them.  Here the female flowers, which are rather bare and uninviting, are borne in a tight globose head at the top of the inflorescence. Male flowers are borne on dense orange-colored spikes below the female flowers.  Brief observations suggested that pollination is accomplished by small flies that land first on the female flower heads, and then crawl down to the spikes of unopened male flowers where they lay their eggs.  Larvae develop within the spikes, feeding on the unopened male flowers, and mature in a few days.  When the new adult flies emerge, the male flowers have opened and are shedding pollen.  The flies are then covered with the sticky pollen and fly off to start a new cycle on another Nypa inflorescence.

Female flowers of Nypa form a dense globose head (left), and appear to provide no nutrition for insects.  The dense male spikes (right), however, provide a place for fly larvae to develop as they feed on the tissues of the unopened male flowers.

Mosses of Central Florida 45. Schwetschkeopsis fabronia

Schwetschkeopsis fabronia (Sull.) Broth. (Myriniaceae) is a creeping moss found at the bases of hardwood trees and on rocks. Leaves are scale-like and more-or-less pressed to the stem. Slender, whip-like shoots may also present.

A dried specimen of Schwetschkiopsis fabronia from the USF Herbarium (M. Newberry, s.n., 18 February 1971, Hillsborough River State Park). The scale-like leaves fold against the stem, making the shoots look like juniper twigs.

Leaf cells are long-oval, slightly bumpy on the upper surface due to projections of the cell walls at the upper end.  The midrib is lacking, very faint, or briefly double.  Spore capsules are upright and more-or-less symmetrical,but have been rarely collected.

The tip of the shoot, showing the short, scale-like leaves.

Light spots at the end of each cell indicate the
 characteristic projections of the thick cell walls.

This species is similar in appearance to Clasmatodon parvulus, but the latter has a distinct midrib.  Papillaria nigrescens is also similar, but with larger leaves, a more distinct midrib, and more elongate leaf cells, each with several papillae.


It is found in Florida from the panhandle southward to Highlands County.  Elsewhere, it is found throughout the eastern U.S., west to Texas, and also in the West Indies and Asia. 

Mosses of Central Florida 44. Herpetineuron toccoae

Wet plants of Herpetoneuron toccoae growing in Macao.
Photo by Li Zhang, posted on the Southern
Illinois University website.

Herpetineuron toccoae (Sullivant & Lesquereux) Cardot (Anomodontaceae) is a creeping moss found on tree bases and rocks.

The leaves spread on both sides of the stem when wet, like other common mosses, such as Isopteryigium, but roll inward and press to the stem when dry.  The leafy shoots also tend to curve to one side when dry.  The leaves also have a distinct midrib, which is somewhat wavy as it approaches the toothed tip. Leaf cells are ovate-angular. It is not known to produce spore capsules in the U.S.

The midrib of the leaf is a bit wavy toward the slightly toothed tip. From a
dried herbarium specimen, Griepenburg 130, USF.

This pantropical species occurs throughout the southeastern U.S., north to Illinois,  and has been reported from Arizona.

In Florida, it has been reported from Franklin Co and spottily in counties along the Gulf  Coast as far south as Hillsborough County.

Leaf cells are oval to angular.

Dried plants. Photo by Blanka Shaw, posted on Consortium of North
American Bryological Collections website.

What's killing our trees?

"Our industrial society with its attendant air pollution is slowly killing our forests, as it has the forests of eastern Europe, weakening and stressing trees, and making them more susceptible to cold winters and attack by pathogens."  Paul Donahue, in Tree Death and Forest Decline.

Dying forests in eastern Europe. Photo by Lovecz, posted on Wikimedia Commons. 

Forests in the eastern U.S., the Rocky Mountains, and California are all seeing massive death of forest trees.  This in turn adversely affects the survival of other plants, as well as of animals dependent on those trees, and biodiversity is seriously diminished.  Yet there are misconceptions, put out deliberately by special interests or arising from ignorance, about what exactly is killing our forests. 

Donahue continues:

"One criticism often leveled by opponents of stricter air pollution standards is that acid rain or other pollutants don't kill trees, that they are actually killed by cold winters or by insects or fungus or some such agent." 

Those who lobby for relaxing pollution standards are using carefully selected facts out of context to support a particular agenda (one of the tools of pseudoscience). It is true that the trees in forests like those above are killed by insects, pathogens and extreme weather, but what is carefully ignored is the fact that such death is greatly increased after the trees have been seriously stressed or weakened by air pollution or changing climate patterns.

In the eastern U.S., as discussed in detail by Donahue, the immediate cause of death has often been severe weather, but trees that have been weakened by acid rain are more prone to damage than healthy trees.  Acid rain results from burning sulfur-containing fossil fuels by industry and from the nitrogen oxide component of automobile exhaust.

In the Rocky Mountains, the Sierra Nevada, and elsewhere in the west, the Mountain Pine Beetle is often blamed.  But this a native species of insect that has been here for thousands of years.  Beetle larvae overwintering below the outer bark of the trees are normally killed by cold weather, keeping the populations under control. They are having a much greater impact now because of higher than normal temperatures and lower rainfall in the past ten years, which also stresses the trees. These changes are part of overall global climate change. 

There is a misconception about climate change, voiced frequently by ignorant government officials, that it will be expressed as a uniform and consistent warming everywhere.  Climate change actually results in a complex array of disruptions that include more temperature and precipitation extremes, both up and down.  So vicious winter storms and extreme low temperatures are part of that disruptive pattern.

The planet is indeed warming overall, as is evident in the melting of the polar ice caps, which in itself will result in complex repercussions in oceanic currents and climate patterns, as well as the rising sea levels that threaten coastal human populations and entire low-lying nations.

"Those who deny the existence of climate change and rising sea levels, who want to do away with environmental protection agencies, who oppose treaties on clean air and reduction of carbon emissions, and who want to open up national parks and other wild lands to mining and other economic exploitation, just don't get it, and must be rejected."

This quote is from my October 2016 essay on endangered species and population growth.  Unfortunately, the fears expressed have been chillingly born out. The current governmental leadership in the U.S. is moving rapidly backwards on issues of air quality, climate change, and protection of public lands.  

Americans have another opportunity in the upcoming congressional elections to choose more environmentally supportive representatives.  Can those of us who understand and respect science, and who care about the environment and biodiversity, make a difference?

Given the many highly publicized and polarizing issues grabbing voter attention this year, it may seem hopeless.  But even if we can tip the scales on some tight congressional elections, even helping elect one or two conscientious representatives, we can make a difference.  You can help in a number of ways:

ASK your representatives or candidates what their stand is on air quality standards and other environmental issues.

EDUCATE your current representatives about important environmental issues and urge them to do the right thing.

If they will not be educated, REPLACE them.  Support candidates who understand the issues and will stand up for them.

VOTE for the best available candidates, Democrat or Republican.  

Though environmental protection has in recent decades has been associated primarily with the Democratic Party, an exchange of letters in a recent Sierra Club Magazine demonstrated that many conservatives also cherish our natural heritage and support the Club's fundamental mission.  This was expressed some time ago in a post from the Missouri chapter of the Sierra Club (click here).  In fact, an organization called Republicans for Environmental Protection (now called ConservAmerica) was established in 1995.  

The primary elections in both parties are the first opportunity to bring better candidates forward.  Republican candidates who support the environment particularly need support.

If you are among the many readers of this blog who do not reside in the U.S., do what you can in your own elections when they come up, and best of luck.  All nations must work together to protect our global ecosystem.

Mosses of Central Florida 43. Micromitrium

There are three species of Micromitrium (Ephemeraceae) in our area: M. megalosporum Austin

Micromitrium tenerum at a drying pond edge.  Permission pending from
Okayama University of Science, http://www1.ous.ac.jp/garden

M. tenerum (Bruch & Schimp.) Crosby and M. synoicum (James) Austin.  These are tiny short-lived plants that form sparse colonies on bare soil along drying pond edges.  The plants form rosettes with a single, globose sporangium nestled among the leaves.  Their leaves lack a midrib and the leaf cells are elongate, somewhat curved (worm-like) and smooth.

They are similar to Ephemerum crassinervium, which is in the same family, but that species has leaves with  distinct midribs, more ovoid capsules, and papillose cells near the tip of the leaf.

The ranges of the three species overlap, as they all occur throughout eastern North America. M. tenerum has been also reported from British Columbia, and M. synoicum from Oregon.  In Florida, they are all found primarily in the panhandle region, with reports from as far south as Polk County. None are collected very often, however, as they are short-lived and hard to see.

In M. megalospermum the leaves are broadly ovate and the spore capsule opens irregularly, while in M. synoicum and M. tenerum the leaves are lance-shaped, and the capsules open along a distinct ring around the middle or above.

In M. synoicum the leaves are erect, with smooth, somewhat incurved margins and have distinct stems below the crown of leaves, while in M. tenerum the leaves are spreading, with flat margins, and teeth at the tips, and the plants are stemless.