The abnormal forms of this species which sometimes manifest themselves are very singular; the sporangium has a tendency to dilate, becoming funnel-form or even salver-shaped, the stipe shortening and even disappearing. I have a large specimen which superficially resembles some lichen, a _Physcia_, for example; the sporangia are pressed down, flattened out, extremely irregular, and in many places confluent; the rudimentary stipes are hidden beneath the leafy expansions. In all the forms, however, may be uncovered the spiniform tubules mingled with the slender threads. This is _Trichamphora oblonga_ B. & C. _Tilmadoche oblonga_ of Rostafinski's monograph, and _Physarella mirabilis_ Peck. V. CYTIDIUM, Morgan. Gen. nov. Sporangium globose or rarely ellipsoidal, stipitate; the wall a thin membrane, with an external layer of minute granules of lime, rupturing irregularly. Stipe more or less elongated, tapering upward and entering the sporangium as a columella. Capillitium of slender tubules, arising from the columella, repeatedly branching and anastomosing to form a regular net-work, the extremities attached on all sides to the wall of the sporangium, the tubules containing at intervals nodules of lime. Spores globose, violaceous. This genus is readily distinguished from _Physarum_ by the columella, which gives origin to the capillitium; this feature indicates a relationship to _Didymium_ and to _Lamproderma_. §1. EUCYTIS. Sporangium globose, the columella not reaching its center. 1. CYTIDIUM PULCHERRIMUM, B. & R. Sporangium globose, stipitate; the wall a thin lilac-tinted membrane, with a dense closely adherent layer of granules of lime, dark purple or wine-colored. Stipe long, erect, dark purple to purplish black, tapering upward and entering the sporangium as a slight obtuse columella. Capillitium of slender lilac tinted threads, forming a dense net-work of very small meshes, with slight expansion at the angles; the nodules of lime very small, numerous, dark purplish or vinose in color, ellipsoidal or obtusely angular. Spores globose, even, lilac, 7-9 mic. in diameter. Growing on old wood. Sporangium .4-.5 mm. in diameter, the stipe two or three times as long; the lime-nodules about the size of the spores. The purple stain, which the sporangia leave on white paper, is made by the granules of lime; the spores color the paper violet. _Physarum pulcherrimum_ B. & Rav., and _P. atrorubrum_ Peck.