349 
Apr. 28,1923 Species of Fusarium Isolated from Potato Tubers 
advance was made with some of them when grown on sterilized tomato 
stems and leaves. 
In order to see what effect age and medium had on spore characters, 
three species, each typical of a group, were chosen and about lo photo¬ 
graphs were taken of them, grown on different media and at different 
ages. Our conclusions are indicated on page 354. 
MICROSCOPIC NOTJ^S 
The only key published which includes the greater number of Ameri¬ 
can species of Fusarium is Sherbakoff's and it was therefore used 
as a basis for this work. In determining the various sections this key 
was very useful, but owing to the fine distinctions made between species 
and especially between varieties much difficulty was experienced in 
identifying an unknown culture. 
In order to seciure the necessary data for the identification work 
microscopical study was made of all cultures grown on hard oak agar 
and on lima bean agar, in addition to the data secured from our micro¬ 
photographs of the cultures grown upon the same media, but under 
somewhat different conditions. The cultures grown on hard oat agar 
were about 15 weeks old and had been kept in the refrigerator at 10® C. 
The cultures grown on lima bean agar were about 4 weeks old and had 
been kept in a dark incubator at about 21® C. 
As with the series of cultures used for the microphotographs, we had 
difficulty here also with certain ones not fruiting; and additional notes 
were made for certain cultures at about 4 weeks of age when grown on 
potato glucose agar and at various ages, depending upon the organism, 
when grown on tomato stems, potato plug, and lima bean agar. 
In Siese examinations particular care was taken to include some 
mycelium in order to determine whether or not chlamydospores were 
present, for in the photographic work it was natural to select a field 
filled with spores rather than one filled with mycelium, and the presence 
or absence of chlamydospores, which character Sherbakoff used con¬ 
siderably, was often overlooked in the earlier studies, 
lil^DIA US^D 
A limited number of media was used in our work, for the concensus 
of opinion of those investigators who have used a large variety, notably 
Smith and Swingle (jp), Apple and Wollenweber (2), and Sherbakoff 
{18), seems to be that little is gained from so doing. Sherbakoff beheved 
that all important characters were brought out on hard oat agar, certain 
vegetable stems, tuber plugs, and potato agar containing about 5 per 
cent glucose. We followed the suggestion of Sherbakoff but used a 
few additional media. The formulas of the media follow: 
Oat agar. —One hundred gm. rolled oats were put in 1,000 cc. of water 
and cooked for an hour in an Arnold steamer whidi varied in temperature 
from 50° to 75° C. 
The product was strained through cheesecloth and the volume of 
liquid was brought up to 1,000 cc. Thirty gm. of agar were added, 
and the mixture was put in the autoclave and the pressure allowed to 
rise gradually to 15 pounds, where it remained for 15 minutes. The 
material was then tubed, and the tubes were plugged and autoclaved. 
