EVANS—THE NORTH AMERICAN SPECIES OF ASTERELLA. 273 
sparingly, but never forming an actual reticulum; the fine markings, on the 
contrary, are made out with difficulty, although a careful search will usually 
demonstrate their presence in some part of the wall. In the specimens collected 
by Barnes and Land (nos, 121 and 671) these conditions are almost reversed ; 
the fine lines here are everywhere distinct and sometimes form an irregular 
reticulum, but the folds are difficult to see, although the distinct crenulations 
at the periphery show that such folds must be present. It was thought at first, 
from a study of these two diverse spore types, that two species might be repre- 
sented, but the close agreement between the specimens in other respects seems 
to preclude this idea. 
Although A. pringlei shares certain characteristics with A. tenella and A. 
ludwigii, it would hardly be possible to confuse them. The three species agree 
in general habit, in their method of branching (which is normally by forking), 
and in their undivided dorsal air chambers, each opening by an epidermal pore. 
A. pringlei, however, in spite of growing in damp localities, shows a certain 
tendency toward xerophytism in having these dorsal chambers high and narrow, 
the more deeply situated chambers being very small. The green tissue thus 
stands in rather sharp contrast to the much looser tissue of the other two 
species, where the chambers are larger and approximately isodiametric. The 
species is further distinguished by the thickened radial walls of the cells en- 
- circling the pore, by the lack of cells containing oil bodies in the epidermis, by 
the thin unpitted walls of the compact tissue, by the autoicous inflorescence, 
and by the dark and almost opaque spores without a coarse reticulum. In 
both A. tenella and A. ludwigii the cells encircling the pore have thin radial 
walls, cells containing oil bodies are present in the epidermis, the cells of the 
compact layer usually show pitted walls, the inflorescence is paroicous, and 
the spores are yellow or pale brown, translucent, and covered over (at least 
on the spherical face) with a coarse reticulum. The remarkable appendages 
of the ventral scales bear a certain resemblance to those of A. tenella, espe- 
cially when teeth are present, but these appendages are larger and more uni- 
formly sharp-pointed, and their teeth are usually more spinelike in appearance. 
The slime papillae on the appendages are also a distinctive feature, no such 
papillae being present on the mature appendages of A. tenella. 
4. Asterella palmeri (Austin) Underw. 
Fimbriaria palmeri Austin, Bull. Torrey Club 6: 47. 1875. 
Fimbriaria nudata Howe, Erythea 1: 112. 1893. 
Asterella nudata Underw. Bot. Gaz, 20: 61. 1895. 
Asterella palmeri Underw. op. cit. 63. 1895. 
Thallus green but more or less pigmented with purple on the ventral surface 
and along the margin, mostly 0.5 to 1 cm, long and 2 to 4 mm, wide, broadened 
out on fertile plants, more or less concave, especially when dry, the undulate 
and crispate margins becoming strongly incurved and somewhat scarious, 
branching by forking, the keel broad and rounded; epidermis composed of thin- 
walled cells without trigones, averaging about 35 X 25 w; pores more or less 
elevated, measuring (with their surrounding cells) 75 to 90 » in length and 60 
to 70 » in width, surrounded by 6 (sometimes 4, 5, or 7) series of cells with 2 
cells in each series, the cells next the opening with more or less thickened 
radial walls; cells with oil bodies not observed in the epidermis, otherwise as 
in A. tenella; green tissue rather compact, the air chambers in 3 or 4 layers (in 
the median portion), those of the dorsal layer elongated vertically and much 
higher than the others, not subdivided, each with an epidermal pore; compact 
1103892—20——3 
