EVANS—THE NORTH AMERICAN SPECIES OF ASTERELLA. 271 
wigit tend to show a less luxuriant development than those of A. tenella, and 
the thallus often appears simple on account of the death of the older parts. 
3. Asterella pringlei Underw. 
Asterella pringlei Underw. Bot. Gaz, 20: 64. 1895. 
Fimbriaria pringlei Stephani, Bull. Herb. Boiss, 7: 96, 1899, not Stephani, 
Rev. Bryol. 36: 139. 1909. 
Thallus sometimes green throughout, becoming brownish or purplish with 
age, but usually somewhat pigmented with purple even when young, especially 
on the ventral surface, mostly 1 to 1.5 cm. long and 3 to 5 mm. wide, plane or 
slightly concave, with thin, undulate, more or less crispate and crenate mar- 
gins, branching most frequently by forking, more rarely by apical innovations, 
apparently never by ventral outgrowths, the keel broad and rounded; epidermis 
composed of thin-walled cells without trigones, averaging about 40 X 25 4g; 
pores somewhat elevated, mostly isodiametric (at least in the median portion), 
measuring (with their surrounding cells) 40 to 60 uw in diameter, surrounded by 
4 to 6 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 compact below, looser above, 
the air chambers in 4 or 5 layers, those of the dorsal layer larger and higher 
than the others, not subdivided, each with an epidermal pore; compact tissue 
occupying about three-fifths the thickness of the thallus in the median portion, 
thinning out gradually or abruptly on the sides and extending from one-half 
to two-thirds the distance to the margin, composed of cells with thin unpitted 
walls; mycorhiza not observed; ventral scales contiguous, not reaching the 
margin, usually more or less pigmented with purple, ovate, the cells containing 
oil bodies mostly 1 to 3; appendages borne singly or rarely in pairs, broadly 
subulate and not constricted at the base, often hyaline, mostly 0.7 to 1 mm, long 
and 0.15 to 0.45 mm. wide at the base, the margin entire or irregularly spinose- 
dentate, the teeth mostly 1 to 5, 1 to 6 cells long and 1 or 2 cells wide at the 
base, each tooth as well as the acute to short-acuminate apex tipped with a 
more or less persistent slime papilla, sessile papillae of a similar nature often 
present also, the cells throughout appendage mostly 40 X 30 uw; inflorescence 
autoicous; male inflorescence consisting of a long and narrow median cluster of 
antheridia, not surrounded by paleae, borne on an ordinary branch and not 
limiting its growth, the ostioles long and slender; peduncle naked, arising from 
the apex of a more or less elongated branch, yellow to brown, not pigmented 
with purple, mostly 1 to 1.5 cm. long; disk of receptacle mostly 3 to 4 mm. 
across, green to purple, hemispherical, covered with low and coarse rounded 
tubercles, the lobes mostly 4, short but distinct, extending obliquely downward, 
the margins and the involucre entire or nearly so; pseudoperianth mostly 12 
to 16-cleft, white or pale, the divisions lanceolate, coherent at the apex; capsule 
circumscissile above the middle by a jagged line, the small operculum coming off 
in one piece; spores dark brown, sometimes almost opaque, mostly 80 to 120 yu in 
diameter, with a wing 6 to 8 » wide along the edges, the entire surface covered 
with a system of fine and irregular darker ridges 1 to 2 uw high, on a paler back- 
ground, the ridges sometimes anastomosing and forming an irregular network 
with meshes 2 to 4 w across and sometimes not, the surface sometimes showing 
in addition a system of low and broader folds about 4 » high and more or less 
anastomosing but never forming a network, the periphery of spores appearing 
coarsely or finely crenulate; elaters brown, more or less curved, mostly 200 to 
220 uw long and 12 to 16 » in diameter, tapering slightly toward the rounded ends, 
