STUDIES IN THE MORPHOLOGY OF RICCARDIA PINGUIS 
Amos M. Showalter 
(Received for publication June 20, 1922) 
Riccardia pinguis (L.) S. F. Gray is found rather sparingly along the edge 
of the marsh next the wooded upland south of Lake Wingra (Madison, Wis¬ 
consin). The thalli grow on fallen willow canes, on the bases of standing 
willows, on the black mud, and occasionally on fallen leaves. In this 
locality they are well shaded during the summer when the willows and oaks 
are in full foliage, but are partly exposed during the fall and early spring. 
Plants of this species are somewhat more abundant on the railroad 
right-of-way through the swamp prairie bordering Lake Waubesa and ex¬ 
tending westward for about a mile. At this station the thalli grow on the 
mud and cinders and more rarely on the roots and stubble of grasses. The 
grasses stand one half to one and one half meters high and form a fairly 
thick shade over the thalli during the summer months, but are burned off 
annually in the fall or spring. Numerous searches in the swamp on either 
side of the railroad have revealed no plants beyond the limits of the annual 
burning of the grass. 
In June, 1921, before the latter station had been discovered, the low 
prairie in the vicinity of Roby, Indiana, about twenty miles from Chicago, 
was visited in the hope of obtaining material for cytological study. Plants 
were found in this region growing chiefly on decaying leaves about the bases 
of very small willows scattered through the more swampy portions of the 
prairie. This material was not in thriving condition because of insufficient 
moisture, and only a small collection was made. 
At all these stations the plants are protected from the summer sun but 
are favored with nearly full sunlight during the fall and early spring—the 
seasons during which vegetative growth appears to be most rapid. It was 
further observed that plants exposed, by tramping of the grass, to the 
August sun quickly succumbed. 
Field and Culture Observations 
The first collections of plants for this study were made in the spring of 
1920 from the region of Lake Wingra and consisted of only a few dozen 
thalli. These plants were used to start greenhouse cultures which grew 
very well during the summer and early fall of 1920, but later became con¬ 
taminated with blue-green algae and had to be discarded early in the follow¬ 
ing winter. These cultures were grown on a thin layer of leaf mold over a 
substratum of sand in shallow wooden boxes standing in a tray of nutrient 
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