266 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
show a wide range of variation, especially with respect to the margin and apex. 
The margin, for example, may be quite entire or it may be more or less dentate, 
the teeth varying from vague crenations to distinct lobelike structures, 3 or 4 
cells long and 2 or 3 cells wide at the base. With regard to the apex, the acute 
condition seems to be the most usual, but obtuse or even rounded apices may 
often be demonstrated. In spite of their fairly large size the ventral scales’ 
are very delicate; along their margins scattered and short-lived slime papillae 
may often be detected, even on the appendages, and the pigmentation some- 
times extends from base to apex. The appendages, moreover, sometimes occur 
in pairs. Stephani’s description of the spores as “grosse lobato-cristatae ” 
hardly implies their reticulate surface markings, and his account of the 
pseudoperianth as “hyalina” seems to ignore the purple pigmentation which it 
often shows. These, however, are points of minor importance, 
Since there are no other species of Asterella in eastern North America, it is 
usually easy to recognize A. tenella in the field, even when sterile, The plants 
in most cases are distinctly aromatic and this will help to separate the species 
from the more robust Reboulia hemisphaerica, while the delicate and incon- 
spicuous scale appendages are very different from the large and prominent ap- 
pendages of Grimaldia fragrans, which usually form a conspicuous cluster at 
the apex of the thallus. The outlines of the dorsal air chambers can usually 
be seen with the aid of a lens in the Asterella but not in the other two species; 
and the flat thallus, showing little tendency to become involute upon drying, 
is also distinctive. | 
2. Asterella ludwigii (Schwaegr.) Underw, 
Marchanita tenella Retz, Fl, Seand. Prodr, ed. 2. 270, 1795, not L. 1753. 
Marchantia polycephala Schleich. Cat, Pl, Helv, ed. 2. 31. 1807, nomen nudum. 
Marchantia pilosa Wahl, Fl, Lapp. 399. 1812, not Hornem, 
Marchantia ludwigit Schwaegr. Hist. Musc. Hep, Prodr. 88, 1814. 
Marchantia gracilis F, Web. Hist. Muse. Hep. Prodr. 105. 1815. 
Marchantia nana Schleich. Cat. Pl. Helv. ed. 4. 1821, nomen nudum. 
Fimbriaria nana Lindenb. Noy, Act, Acad, Caes. Leop, Carol, 14: Suppl. 109. 
1829. 
Fimbriaria pilosa Tayl. Trans. Linn. Soc, 17: 386. pl. 13, f. 8. 1887. 
Fimbriaria schleicheriana Corda; Nees, Naturg. Eur. Leberm. 4: 273, 1838, 
as synonym. 
Dictyochiton pilulare Corda, op. cit. 280. 1838, as synonym, 
Fimbriaria gracilis Lindb. Not. Sillsk. Faun. Fl. Fenn, Férh. 10: 282. 1868. 
Asterella pilosa Trevis. Rend. Ist. Lombardo II, 7: 785. 1874. 
Fimbriaria ludwigiit Limpr.; Cohn, Krypt. Fl. Schles, 1: 340. 1876. 
Hypenantron gracile Trevis. Mem, Ist. Lombardo IIT, 4: 440. 1877. 
Hypenantron nanum Trevis. loc. cit. 
Hypenantron pilosum Kuntze, Rev. Gen, Pl. 1:89. 1891. 
Asterella gracilis Underw. Bot. Gaz. 20: 61. 1895. 
Asterella ludwigit Underw. loc. cit. 
Fimbriaria macounii Stephani, Bull. Herb. Boiss. 7: 99. 1899. 
Thallus green, often more or less pigmented with purple, especially on the 
ventral surface and along the margin, mostly 0.5 to 1.5 em. long and 1 to 2 mm. 
wide, but often 3 to 5 mm. wide on broadened-out fertile plants, plane or 
somewhat concave, with thin undulate margins, sometimes more or less in- 
curved when dry, branching regularly by forking, the keel broad and rounded ; 
epidermis composed of cells with thin or slightly thickened walls, usually with 
more or less distinct trigones, averaging about 25 X 20 uw; pores slightly ele- 
vated, averaging (with their surrounding cells) about 80 X 65 w, Surrounded by 
