1200 Wisconsin Academy of Sciences, Arts•, and Letters. 
spores. Added to these difficulties is the fact that the mycelium 
is very much twisted and branched and that the nuclei are very 
small and not at all easy to differentiate. 
I have studied at various stages of development the following 
species: IJstilago levis, II. Zeae ,U. Triaici, II. nuda, Urocystis 
Anemones, Doassansia Alismatis, D. deformans, and Entvloma 
Hymphaeae. As my methods were different for almost every 
species I shall describe them as I take up the individual forms. 
I desire to thank a number of mycologists for material, par¬ 
ticularly Dr. J. I. Davis of Racine, Wis. My thanks are due 
also to Prof. R. A. Harper at whose suggestion the work was 
undertaken and on account of whose assistance and encourage- 
/ 
ment it was completed. 
IJstilago levis (Kell. & Sw.) Magn. 
Ustilago levis has been our most common species of oat smut 
during the past three years. As it is available at any time dur¬ 
ing the summer and the spores are viable for a long time it is on 
the whole a very favorable smut for cytological study. 
In order to obtain large quantities of the conidia for the pur¬ 
pose of infecting seedlings it was necessary to resort to bacterio¬ 
logical methods. A very high dilution of the spores in sterile 
water was plated out in 1 % beerwort agar and kept at a temper¬ 
ature of about 12° C., a refrigerator being used. This temper¬ 
ature seemed to prevent the too rapid growth of other species of 
fungi such as moulds and Penicillium while it did not hinder so 
much the development of the smut conidia. After three or four 
days, small white colonies appear on the plates; these spread in 
the film of water that always covers agar plates and were al¬ 
lowed to grow until they had attained the diameter of a centi¬ 
metre. These colonies can be obtained as practically pure 
growths of conidia and were used in this condition for infection 
purposes, or they could be still further increased in quantity by 
inoculating flasks of liquid beerwort and allowing them to stand 
for a few days. In most cases the colonies themselves were used 
for inoculations as they were much easier to handle and the lo¬ 
cation of the infected area on the seedling could be more readily 
