Reported from England on beds of leaves or straw; in Portugal Dr. Torrend finds it on or in dead leaves of Agave americana! Evidently an American species, and belonging to arid regions; its occurrence in England surprising!

14. Didymium annulatum Macbr. n. s.

[Plate XX.], Figs. 4, 4 a.

Sporangia small, scattered, annulate, not only without columella but perforate when the stipe is broken, umbilicate above and below, grey, coated with crystalline frustules, opening irregularly about the periphery; stipe white, or pallid, fluted, tapering upward from a distinct hypothallus; capillitium scanty consisting of delicate, sparsely branching threads, the branchlets anastomosing more or less at length, attached to the peridial wall, radiating from the rim of the slightly depressed top of stipe, without special thickenings save at the insertion of the ramules a triangular enlargement is usual and of dark or pallid shade; spores smooth; however they show three or four spots on the hemisphere and other minute but variable markings; 9–10 µ. Seattle, Washington.

Differs from D. nigripes in color of the stipes, capillitium, spore-diameter, etc.

15. Didymium dubium Rost.

Fructification wholly plasmodiocarpous, snow-white, small, 2–6 mm., flat and thin; the outer wall double, membranous within, calcareous-crystalline without; columella none; capillitium simple of rather thick, vertical, brown threads, sparingly united laterally, and only occasionally furcate at the ends, especially above; spores minutely spinulescent, violaceous pale, 12–15 µ.

Massee thought English specimens out of harmony with the original description and gave them a new name. To refuse this, Lister enlarges the range of spore-measurements and disregards some of Rostafinski's specifications as to capillitium. Our specimens are as described.

Bohemia. England. Shores of Lake Okoboji, Iowa.