90.
1824. _Arcyria nutans_ Grev., _Fl. Edin._, p. 455.

Sporangia crowded, cylindric, about 2 mm. high when unexpanded, pale
yellow or buff, short-stipitate or sessile by an acute base; peridium
wholly evanescent, except at the base, where persists the shallow,
colorless, often inwardly spinulose, plicatulate calyculus; stipe very
short or wanting; hypothallus thin but usually in evidence; capillitium
expanding to great length, forming an extremely flexile, plumose,
pendulose open network of pale ochraceous tint, the threads 3-4 mu in
thickness, adorned with spinules, sharp edged transverse plates
sometimes rings, the surface especially marked by an indistinct
reticulation; spore-mass buff or ochraceous, spores by transmitted light
colorless, smooth or nearly so, 7-8 mu.

This elegant species is not rare in undisturbed woods, especially on
fallen willows. The expanded capillitia are very soft and plume-like,
waving and nodding, very lightly attached below to the centre of the
peridial cup. The capillitium threads are rough, with irregular spines
and sharp-edged transverse plates, occasionally extending to form rings.
Resembles the first species somewhat in habit, size, and the spinescent
capillitium, but the resemblance is superficial only. The color is at
once diagnostic, and the capillitium is after all entirely different.
Not uncommon; Canada to Mexico; Maine to California; probably
cosmopolitan.

Bulliard's figure determines the synonymy. Persoon called the form _A.
flava_, because Bulliard had missed the genus.

4. ARCYRIA VERSICOLOR _Phillips._

1877. _Arcyria versicolor_ Phillips, _Grev._, V., p. 115.
1877. _Arcyria vitellina_ Phillips, _Grev._, V., p. 115.

Sporangia gregarious or more or less crowded, pyriform or clavate,
dingy, olivaceous yellow, becoming reddish, stipitate; peridium
membranous, largely persistent below, where it gives rise to the deep,
goblet-shaped calyculus; stipe strand-like, weak, sometimes wanting,
concolorous with the peridium; hypothallus prominent or venulose;
capillitium only slowly expanded, bright golden yellow or orange, the
threads rather broad, about 4 mu in diameter, regular, even, elegantly
branching, adorned with abundant short spines or warts, very small and
evenly distributed, the whole net anchored in the bottom of the vasiform
calyculus; spore-mass yellow, by transmitted light pale or nearly
colorless, smooth, about 10 mu.

This beautiful species is