VoL. XIV 
THE BRYOLOGIST 
JULY 1911 
No. 4 
SOME STAGES IN THE DEVELOPMENT OF PELLIA 
EPIPHYLLA. 
HELEN E. GREENWOOD. 
[Presented at the Sullivant Moss Society Meeting, Minneapolis, Dec. 28, 1910.] 
Pellia epiphylla, one of the more common hepatics in this locality, 
grows on the ground in damp shaded places, its favorite location be- 
ing on the banks of streams, either submerged or just above the water 
line, or more often extending several feet from the water’s edge. It 
may be found in smaller patches on damp roadsides in close prox- 
imity to Anthoceros and Blasia, and scattered plants are sometimes 
found on boggy soil in pastures and swamps. 
The slightly fleshy thallus has no suggestion of leaves, and varies 
from a simple oblong shape to one more or less sinuate, lobed and 
forked. (PL VIII, figs. 4, 5, 6. ) The plants tend to grow in masses and 
sometimes will cover the soil for several feet if no other plant growth 
crowds them out. The ends of the plants overlap each other in 
shingle fashion (PI. VII) doubtless to prevent too rapid evaporation of 
moisture. 
This crowding together of the plants gives rise to a great variety 
of shapes. Those growing underneath or in more shaded positions 
take on a narrow, slender shape (Plate VIII, figs. 4a, 4b) while those 
having a greater exposed surface fork and fork again and broaden 
out horizontally (Figs. 5, 6a). 
The color, texture and fruiting tendency of the thallus, varies 
somewhat according to the place of growth, this difference seeming 
to be governed by the amount of moisture available. The plants 
growing in drier locations are of a pale, dull-green color and the re- 
gion of the costa is often characterized by a reddish or purplish tinge. 
These plants are thinner and more solid in texture than those growing 
in very moist situations. The plants growing close to the water’s 
edge or on very wet soil have, in comparison, a rank luxuriant growth, 
the cell structure of the plant body being less compact. These plants 
have a richer, brighter green color with no trace of the purple tinge 
noted above. 
Although the plants in moist situations have a more vigorous 
growth, they are far more likely to be sterile than those of drier loca- 
tions, the latter being almost invariably well fruited. But when those 
in moist situations do form fruiting organs they are much farther ad- 
vanced at the same season than those of a drier habitat. 
The structure of the thallus is comparatively simple. A longi- 
tudinal section shows a slight degree of cell differentiation and a lack 
The May Bryologist was issued May 19, 1911. 
