Sporangia ovoid or short cylindric, crowded or gregarious, dull red or brownish, stipitate; stipe about equal to the sporangium, dark brown or black; hypothallus well developed, membranous, yellowish brown continuous; calyculus large, wide and shallow, smooth; capillitium centrally attached, when fresh, brick-red in color, fading on exposure, the threads of uneven size, those above 6-7 mu, below 3 mu, abundantly branching, marked by conspicuous reticulations formed by the intersection of numerous vertical plates or ridges; spore-mass reddish, spores by transmitted light pale ochraceous, distinctly warted, 10-12 mu. This species is distinguishable at sight by the peculiar color and form of the sporangia. Mr. Durand in _Bot. Gaz._, XIX., pp 89, 90, gives a careful study of the form. The same author declares the dehiscence circumscissile. We cannot distinguish _A. aurantiaca_ Raun. from the present form. Rare. Maine, New York; Monterey, California. 8. ARCYRIA DENUDATA (_Linn._) _Sheldon._ PLATE II., Figs. 5, 5 _a_. 1753. _Clathrus denudatus_ Linn., _Syst. Nat._, 1179. 1794. _Arcyria punicea_ Pers., _Roem. N. Mag. Bot._, I., p. 90. 1895. _Arcyria denudata_ (Linn.) Sheld., _Minn. Bot. Studies_, No. 9, p. 470. Sporangia crowded or gregarious, ovoid or short cylindrical, tapering upward, red-brown, stipitate; peridium evanescent except the plicate calyculus; stipe about equal to the expanded capillitium, concolorous, plicate or striate, ascending from a small hypothallus; capillitium attached to the whole inner surface of the calyculus and connate with it; hence not deciduous, bright red or carmine when fresh, turning brown or paler with age, the threads even, about 3 mu adorned with a series of rather distant cogs or half rings, which form around the thread a lengthened spiral; spore-mass red or reddish brown, spores by transmitted light colorless, nearly smooth, 6-8 mu. This species is easily distinguished from all other of similar tints by the attachment of the capillitium. In this respect it corresponds with the following species. In the adornment of the threads it is like _A. incarnata_. It is by far the commonest species of the genus, and probably enjoys a world-wide distribution. To be found at all seasons on the lower side of fallen sticks, _Populus_, _Tilia_, etc. Micheli, Pl. XCIV., shows that he had the present species. The description given by Linne is worthless, but helped out by Micheli, and several other authors of the eighteenth century, who take the trouble to describe the species, but still give the Linnean binomial as a synonym; we may give Linne here the credit. As a matter of fact, Batsch under _Embolus crocatus_ first presents an unmistakable description and figure. Maine to the Black Hills and Colorado, and north and west; Alaska to Nicaragua. 9. ARCYRIA CINEREA (_Bull._) _Pers._ PLATE II., Figs. 3, 3 _a_.