Plagiomnium insigne (Mitt.) T.J. Kop.

Habitat

Photo by Shona EllisPlagiomnium insigne can commonly be found growing in humid coastal forests on rotten logs and tree trunks. Additionally, Plagiomnium insigne may be located in swampy areas, alluvial sites, shaded banks, or lawns.

 

 

 


Gametophyte

Overall Structure:

Plagiomnium insigne exhibits an acrocarpous growth form.  The shoots form loose, tall green turfs. This is the largest of Plagiomnium species in British Columbia.

 

 

Leaf Structure:

The leaves are strongly contorted when dry. To avoid desiccation in other species the leaves pull up against the stem, aiding in water retention. Plagiomnium insigne typically grows in shaded and moist areas, thus does not require such an adaptation. In this photo the shoot is moist.

 

 

The leaves are decurrent: both sides of the leaf base extend down along the stem. Plagiomnium insigne apex, whole mount

 

 

 

 

The apex of the leaf is acutely pointed, and the costa has elongate cells. Plagiomnium insigne marginal teeth

 

 

 

The margin cells are elongate and form single teeth. The laminar cells are rounded.

 

 

 

 

Plagiomnium insigne leaf cross-sectionThe lamina is unistratose, while the costa is multistratose.

 

 

 

 

Plagiomnium insigne leaf costa cross-sectionThe costa has a central conducting strand, surrounded by larger parenchymal cells.

 

 

 

 

Stem:

The stem has a wide cortex with a central conducting strand composed of hydroids.

 

 

 

 

 

Rhizoids:

The rhizoids are dark brown, and uniseriate with oblique crosswalls.  Rhizoids do not contain chloroplasts.

Male Gametophyte:

The male gametophytes are easily recognizable by the rosette of leaves surrounding the apex of each shoot.

 

 

 

 

 

The apex of the gametophyte, containing antheridia and paraphyses is surrounded by perigonial leaves. All together, these structures constitute the perigonial head. This arrangement allows for a splash cup mechanism of sperm dispersal.

 

 

 

 

The antheridia are sac-like and contain sperm. The paraphyses are contain chloroplasts, are uniseriate, and sterile.

 

 

 

 

 


Sporophyte

Sporophytes generally mature in the spring. Multiple sporophytes may arise from a single shoot of a female plant.

 

 

 

 

 

Sporangium:

Plagiomnium insigne sporangiumWhen fully mature, the relatively large sporangia are brownish and nodding.

 

 

 

 

 

Plagiomnium insigne sporangium

 

Seta:

The mature setae are bent at their apices so the sporangia appear nodding.