EVANS—THE NORTH AMERICAN SPECIES OF ASTERELLA. 299 
the elaters, noting the frequent occurrence of 2 spirals in the middle and 1 
at each end. 
Stephani, in his description, adds details about the epidermis and green 
tissue, which were not considered in the original account. As in the case of 
A. elegans and certain other species, he alludes to filaments in the air cham- 
bers, but describes them as very short, often reduced to a single cell. In a 
few cases, where he deviates from Gottsche’s description, he introduces incor- 
rect or at any rate misleading statements. He states definitely, for example, 
that the male branches are short, thus giving no idea that they vary in length. 
He states further that the elaters are bispiral and that the spores are reddish, 
63 » in diameter, and lobate-cristate. He thus tells us nothing about the uni- 
spiral and partially unispiral elaters or about the conspicuous reticulations on 
the surface of the spores, although these features were clearly brought out by 
Gottsche and are well shown by the type material, which Stephani doubtless 
examined. The size of the spores is also far more variable than he implies. 
The writer feels considerable hesitation in accepting A. echinella as a valid 
species, on account of its very close relationship to A. elegans. Except for the 
fact that the tubercles of the female receptacle are longer in A. echinella than 
in A. elegans, the two species are essentially alike. This is indicated by the 
descriptions. Even when the features of A. echinella are considered in detail 
for the sake of completeness, no other important differences are brought out. 
Whether it is justifiable to base a species on a single character and especially 
on a character subject to variation is perhaps questionable. It may be noted, 
however, in support of such an action, that the very long tubercles of A. 
echinella certainly give the plants a distinctive appearance and that the known 
ranges of A. echinella and A. elegans do not overlap. There occurs in Mexico, 
moreover, another species, A. lateralis, which is likewise very close to A. elegans 
but which has shorter tubercles. There is no evidence that this species inter- 
grades with A. echinella, and the three species might well be considered as 
forming a series with A. elegans in the middle. Of course later investigations 
may prove the instability of these ideas. 
12. Asterella lateralis Howe. 
? Fimbriaria elegans B beyrichiana Gottsch., Lind. & Nees, Syn. Hep. 565. 
1846. 
? Fimbriaria elegans ¢ obtusata Gottsch., Lind, & Nees, loc. cit. 
Fimbriaria quitensis Spruce, Trans. Bot. Soc, (Edinburgh) 15: 563. 1885, 
as synonym. 
Asterella lateralis Howe, Bull. Torrey Club 25: 189. 1898. 
Fimbriaria lateralis Stephani, Bull. Herb. Boiss. 7: 201. 1899. 
Thallus much like that of A. elegans but more xerophytic in habit, the 
margins more or less incurved when dry and the ventral pigmentation usually 
more intense, mostly 1 to 2 cm. long and 2 to 4 mm. wide, rarely forking, 
almost always ventrally branched, the sexual branches (with rare exceptions) 
very short; epidermis composed of cells with somewhat thickened walls but 
rarely with trigones, averaging about 55 X 28 w; pores distinctly elevated, 
measuring (with their surrounding cells) mostly 120 to 160 » in length and 
90 to 110 w in width, surrounded usually by 8 (sometimes 9 or 10, rarely 4 to 
7) radiating series of cells with 3 or 4 cells in each series, the radial walls 
slightly thickened; cells containing oil bodies as in A. elegans; green tissue 
compact, the air chambers mostly in 3 or 4 layers, similar to those of A. ele- 
gans; compact tissue occupying from one-half to two-thirds the thickness of 
the thallus in the median portion, thinning out gradually on the sides and 
