Sporangia crowded or gregarious, oblong cylindric, ovoid, at first red, becoming yellowish brown, stipitate; the peridium evanscent except the calyculus, which is small and thin, polished; stipe shorter than the expanded capillitium, pale reddish brown; capillitium centrally attached, showing threads of two sorts, those within freely branching, slender, 1-1.5 mu, marked with half-rings or ridges, those on the periphery very different, yellow, broad, 5-6 mu, forming rather dense reticulations, with abundant free tips, acute and often curved, the whole surface here minutely and densely warted; spore-mass reddish yellow, spores by transmitted light colorless, globose, 7-8 mu. The peculiar double capillitium seems to separate this form from the true arcyrias. Some difference in the diameter of the capillitial threads in different regions is not infrequent in the several species of _Arcyria_, but that difference is here emphasized and rendered yet more striking by the peculiar free tips. The present forms bear only the most superficial resemblance to _A. ferruginea_ Saut., with which species it is in some quarters sought to unite it. Very rare. Collected, as noted, nearly fifty years ago in South Carolina by Ravenel, it was more recently (1896) again collected in Maine by the late Professor Harvey. _D._ PROTOTRICHIACAE A single genus,-- =Prototrichia= _Rost._ 1876. _Prototrichia_ Rost., _Mon. App._, p. 38. A single species,-- 1. PROTOTRICHIA METALLICA (_Berk._) _Mass._ PLATE XVIII., Figs. 12, 12 _a_, 12 _b_. 1860. _Trichia metallica_ Berk. Hook., _Fl. Tasm._, 2, p. 168. 1866. _Trichia flagellifera_ Berk. & Br., _Ann. Mag. Nat. Hist._, 3, XVII., p. 56. 1876. _Prototrichia flagellifera_ (Berk.) Rost. _Mon. App._, p. 38. 1894. _Prototrichia flagellifera_ Rost., List., _Mycet. 2nd ed._, p. 206. 1899. _Prototrichia flagellifera_ (Berk. & Br.) Rost., Macbr., _N. A. S._, p. 199. 1892. _Prototrichia metallica_ Mass., _Mon._, p. 127. 1911. _Prototrichia metallica_ Mass., List., _Mycet., 2nd ed._, p. 260. Sporangia sessile, scattered or sometimes crowded, brown, sometimes with a rosy tinge, about 1 mm. in diameter; peridium a thin, transparent, iridescent membrane, bearing in its inner surface the distal attachments of the capillitial threads; capillitium of numerous brown, spirally banded threads, which take origin in the base of the sporangium, become subdivided as they ascend, and are at length attached by their tips to the sporangium wall; spore-mass brown, spores by transmitted light pale, minutely roughened.