230 BULLETIN OF THE BUSSEY INSTITUTION. 
to a Uredo, except in the color of the spores, which are produced free 
in a cell, and are not attached to any mycelium whatsoever. The fun- 
gus we have found abundant from the first of June until the middle of 
October, especially on plants growing in wet places. The spots vary 
in color from a coffee-color to a bright yellow, — the latter being more 
common, —and are nearly circular; so that, when the spores have been 
discharged, as is remarked by Peck, they bear a resemblance to Avcidia 
much more than to Uredo forms. 
To study the development of the fungus, leaves were moistened and 
placed under a bell-glass, and some of the leaf-stalks were placed in 
watch-glasses filled with water. The spots on the leaves in three or 
four hours began to swell, and became reddish orange in color. A 
microscopic examination of the leaves showed that there was no 
mycelium, but that we had to do with a unicellular parasite which 
had invaded certain of the cells of the epidermis, causing them to 
swell to such dimensions as to equal in diameter two-thirds the entire 
thickness of the leaf. Externally, the spots rose in a hemispherical 
form above the surface of the leaf. A section through the discolored 
spots showed that the enlarged and spherically distorted epidermal cell 
was nearly filled by a unicellular parasite, whose contents were, at 
first, slightly yellow and contained numerous oil globules. Later, the 
contents divided into a mass of spores (zodsporangia) which, from 
mutual contact, were somewhat angular, and which were too numer- 
ons to count. In one instance, 200 were counted, and there were still 
more in the sporangium. The diameter of the spores was about .015 
mm., and that of the cell in which they were contained was from 
-18—.20 mm. 
When ripe, the sporangia burst open, and the spores, which had be- 
come reddish orange, were discharged in such quantities as to colour 
the water in the watch-glasses in which they were placed. For a few 
moments after their discharge, they assumed a spherical shape, but soon 
became irregularly four-angled, at the same time losing their reddish 
color and becoming rather transparent. About half an hour later, the 
contents began to divide into a number of distinct portions, and one 
of the four angles of the spore became more and more papillate. The 
internal portions became more distinctly spherical, collected at the apex 
of the spore, and finally burst through and the whole contents of the 
spore were discharged in the form of zodspores which were of irregular 
