EVANS—THE NORTH AMERICAN SPECIES. OF ASTERELLA. 287 
restricted to the ventral scales and contiguous portions of the ventral surface, 
mostly 1 to 2 em. long and 2.5 to 4 mm. wide, plane or slightly concave above 
with thin, slightly sinuous-crispate margins, not incurved when dry, branching 
by forking, apical innovations sometimes present; keel broad and rounded; 
epidermis composed of cells with thin walls but sometimes with more or less 
distinct trigones, averaging about 35 X 25 uw (or a trifle more in shade plants) ; 
pores slightly elevated, measuring (with their surrounding cells) mostly 80 to 
90 » in length and 50 to 65 w in width, surrounded by 7 or 8 (sometimes 6 or 9) 
series of cells with 2 or 3 cells in each series, the radial walls sometimes thin 
throughout, sometimes slightly thickened and showing more or less distinct 
trigones; cells containing oil bodies as in A, tenella; green tissue loose, the 
air chambers in 2 or 3 layers in the median portion, those of the dorsal layer 
larger than the others and sparingly subdivided by supplementary partitions; 
compact tissue occupying about one-half the thickness of the thallus in the 
median portion, thinning out rather abruptly on the sides and extending about 
one-third the distance to the margin, composed of cells with thin unpitted 
walls; mycorhiza sparingly developed; ventral scales small, not overlapping, 
ovate, colorless or somewhat pigmented with purple, entire; cells containing 
oil bodies mostly 5 to 10, scattered; appendages borne singly (always, so far 
as observed), subulate from a broad and unconstricted base, mostly 0.25 to 
0.4 mm, long and 0.12 to 0.18 mm. wide, acute to acuminate, entire, the cells 
mostly 40 to 50 » long and 20 to 25 w wide, occasional cells with oil bodies in 
the basal portion; inflorescence paroicous, the antheridia forming a small and 
irregular median group near the peduncle of the female receptacle, the ostioles 
low; peduncle with scattered slender paleae and a slightly denser cluster at 
the apex, usually green but sometimes purple at the base, about 1 cm. high; 
disk of receptacle mostly 3 to 4 mm. across, flat or nearly so above with a small, 
slightly elevated center, coarsely tuberculate, with low rounded tubercles, 
rugose when dry, normally 4-lobed, the lobes spreading almost horizontally, 
the involucre a thin membrane on the side next the peduncle, not bilobed but 
vaguely sinuate-crenate on the margin, barely reaching the margins of the 
lobes; pseudopcrianth white or yellow, directed obliquely downward, mostly 
8 to 10-cleft, the divisions narrowly lanceolate, connate at the apex; capsule 
yellow, circumscissile above the base by a very irregular line, the operculum 
coming off in one piece; spores yellowish brown, translucent, mostly 55 to 65 p 
in diameter, with wavy wings 8 to 10 » wide along the edges, the entire surface 
(including the wings) covered over with a fine and irregular reticulum formed 
of wavy and zigzag ridges about 1 » high slightly darker than the rest of the 
spore surface, the meshes mostly 1 to 4 » in diameter (rarely up to 6 »), coarser 
folds or ridges not present; elaters pale yellow, variously curved, mostly 180 to 
200 » long and 6 to 8 » wide, tapering more or less toward their blunt ends, 
bispiral throughout or unispiral at the ends, the spirals pale and inconspicuous. 
Growing on banks; known only from Brazil and Mexico. The following speci- 
mens have been examined: 
FEDERAL District oF Mexico.: Amecameca, 1908, Barnes & Land 339 in part 
(Y.; mixed with Targionia hypophylla L.) ; Cafiada Santa Magdalena, Barnes ¢ 
Land 441 (Y.). 
Pursta: Banks along Avenida Hidalgo and path to barranca, Teziutlin, 
Barnes & Land 555 (Y.). 
Brazit: Without definite localities or dates (N. Y.; two specimens, one col- 
lected by Klotzsch, the other by an unknown collector.) 
The type specimens of this fragile species have not been studied by the writer. 
They were collected in Brazil by Sellow, no more definite locality being men- 
