102 Wisconsin Academy of Sciences, Arts, and Letters. 
hattan the grain rusts winter as a mycelium within the host and 
produce spores from time to time as the warmer periods occur. 
In a still more recent paper, Carleton 1 asserts that the uredo on 
Poa pratensis winters alive as far north as Lincoln, Nebr. 
In order to further test and determine in a latitude still 
farther north, the ability of rusts to winter as mycelium and 
uredospores, the writer undertook to follow the history of sev¬ 
eral of our common rusts through the winter of 1902-1903. 
In the fall of 1902, volunteer grain was very abundant in the 
vicinity of Madison and well rusted plants could be easily found 
until late in November. Luring the winter and early spring 
material was gathered from plots of Sclilansted rye and Bed 
Clausen winter wheat on the University Experimental Farm. 
The Poa and oat material was gathered from plots in the city. 
The plots on the University Farm were situated on a piece of 
ground sloping to the northwest. From these plots the snow 
drifted leaving the ground bare during the greater part of the 
winter. The oat and Poa plots were well covered with snow. 
From time to time plants bearing uredospores were taken into 
the laboratory and the spores were germinated in water. These 
water cultures were made within a few hours of the time of 
gathering the material. The dates of collecting and the pre¬ 
vailing temperatures may be taken from the following table. 
Initial letters are used to indicate the particular rust collected. 
There are also shown the maximum and minimum temperatures 
for each day of the month, as indicated at the head of each 
vertical column. Spores were germinated on every date noted 
except in the case of P. poarum collected February 18th. 
i Carleton,—Investigations of Rusts, Bull. 63, Bur. Plant. Ind., U. S. 
Dept. Agric., July, 1904. 
