Wednesday, April 20, 2016

Mosses of Central Florida 15. Physcomitrium collenchymum

Physcomitrium collenchymum forms extensive colonies, and an abundance
of spore capsules, in the wet soil along receding ponds. (Essig 20160328-1)

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

Physcomitrium collenchymum (Funariaceae) occurs along the receding edges of ponds during the dry season, and in other disturbed wet sites.  It evidently completes its life cycle rapidly, producing an abundance of spore-bearing capsules in the interval before the rains fill up the ponds again.
After losing their lids (calyptras) the capsules resemble
 wide-mouthed wine glasses and lack teeth around the margins.  

This species occurs in Florida and in other southeastern states, with outlying records in Kansas and Nova Scotia.  It is distinguished from the related species, P. pyriforme, by its globose, rather than inverted pear-shaped, capsules.  The capsules lack any teeth around the opening, which distinguishes them from many common mosses, such as Isopterygium.

The leaves have a strong midrib and clear, rectangular to angular cells with walls irregularly thickened.  The thickened appearance appears to be due to chloroplasts adhering to the walls.  Leaf cells are smooth, lacking any papillae (hard, pimple-like bumps).  This distinguishes this species from similar-looking members of the Pottiaceae.
The leaves of Physcomitrium have a strong midrib, and large rectangular
cells.
Note: photographs, geographic distributions and information about the naming history and synonyms of this and other mosses are currently being incorporated into the Atlas of Florida Plants.

Adhering chloroplasts give the cell walls a rough, thickened
appearance.