LEAF-SPOT OF ALFALFA AND RED CLOVER. 13 
dipped in 50 per cent alcohol and placed in a solution of 1 part of 
bichlorid of mercury in 1,000 parts of water for 1 to 14 minutes. 
After washing, the fragments were placed separately on slopes of 
2 per cent water agar. After these cultures had been kept three 
weeks at 17° to 19° C., small tufts of mycelium emerged from the 
fragments which had remained free from contamination. The frag- 
ments were then transferred to oat agar. Apothecia appeared two 
weeks Jater, and cultures were started. Success in this imstance seems 
to be due to the relative freedom of these greenhouse plants from 
fungi which quickly enter the host tissue that has been killed by the 
parasite. ; 
CULTURAL CHARACTERS OF SPECIAL MEDIA. 
Only a few of the more common media on which the fungi grow 
‘most readily and show the most striking differences are selected. 
In connection with these descriptions the following facts regarding 
the method of making cultures and their habit of development should 
be kept in mind: 
(1) New cultures are started by placing near the top of an agar slope a 
fragment of a culture which is producing and discharging ascospores abun- 
dantly. The position of the slope should be changed from time to time to insure 
a somewhat uniform distribution of the spores over its entire length. After 
from one to four days the original transfer may be removed to another slope 
and thus serve to start a number of cultures successively. 
(2) The small fungous colonies which arise fruit better and earlier when 
closely crowded together. Yet excessive crowding may delay fruiting. 
(3) Apothecia appear in three to five weeks at favorable temperatures. 
After a period of active spore production lasting from one to two weeks, fur- 
ther spore production takes place only occasionally. ‘Transfer of the stroma 
to new media increases the likelihood of its occurrence but does not insure 
it. The stroma itself continues to grow very slowly. 
Oatmeal agar.—As a culture medium oatmeal agar has proved to be 
the most useful for general culture work, because upon it ascospores 
are produced in greatest abundance. The following description 
applies to cultures kept at 20° to 22° C. 
Pseudopeziza medicaginis: 'The first evidence of growth appears 
about one week after spores are discharged upon the medium. At 
this time the surface of the substrate appears roughened as though 
pushed up into a multitude of minute flat cones. In about two 
weeks the cones are increased in size and show a rusty brown color at 
the center. The color becomes darker at the center of the cone, 
surrounded by a rusty rim. Soon the dark-brown color covers the 
entire slope. If the colonies are not sufficiently close to touch each 
other in three weeks, the color is darker than if the colonies merge. 
At the end of three or four weeks apothecia appear at the center of 
the stromata as small grayish white, often glistening gelatinous 
