Apr. fl8,1933 Species of Ftisarium Isolated from Potato Tubers 
G^NERAI, DISCUSSION OP Ml^HODS 
EFFECT OF MEDIA 
No distinct effort was made to determine the comparative values of 
different media, for in order to determine such values a large number 
of trials should be made on each medium under observation. However, 
the results which we gained from a few trials on a few media may be 
of some value. 
Effect on cuuturau characters. —^The growth made on sweet clover 
stems lacked color. In fact certain cultures (those ordinarily grouped 
under K, a Discolor group, and under D, an Elegans group) which constantly 
produced color on all other media did not exhibit any on sweet clover. 
The growth was scanty in proportion to that on other media. This 
may have been due to the fact that the stems used were old ones which 
had been very dry. However, Sherbakoff (18) notes that the presence 
of the epidermis on stems seems to lessen the development of aerial 
mycelium and to favor production of fewer but better developed sporo- 
dochia. We also found that sweet clover stems seemed to favor tte 
production of sporodochia and pseudopionnotes. A few cultures which 
had not at any time formed sporodociia did so on this medium. The 
sweet clover stems were sometimes covered with a thick, tough layer 
of plectenchymatic-like tissue which seemed never to bear spores. 
The little experience we had with tomato stems suggested that they, 
too, favored the production of spores. However, oiur work with this 
me^um was very limited, as we used it only on refractory cultures. 
Lima bean agar proved to be another medium that did not stimulate 
color production. For instance on Group F (a Martiella group) notes 
taken 12 days after inoculation read, slight appearance of greenish 
blue growth,*' while cultures of the same group growi; on oat at ii days 
showed “various combinations of blues, greens, and purples." The D 
group (an Elegans group) which was mulberry ptu-ple on oat showed 
white or gray on lima bean. 
That series of cultures (p. 350) growing on lima bean which was divided 
and part grown in the diffused light and part in the dark incubator 
showed practically no difference in color production. Only two cultures 
produced color in the dark that did not produce any in the light. The 
amount of mycelium on the lima bean cultures varied somewhat with 
the groups. 
The mycelial growth on potato plug was abundant, and color appeared 
in varying degrees. That is, more color was produced on potato plugs 
than on lima bean or on the stems of sweet clover, but less than on the 
oat or potato glucose agars. Thick, tough layers of plectenchymatic 
tissue formed over the tuber plugs, as it did over the stems of sweet 
clover, but sporodochial growth was rare. 
The greatest variety of colors was produced on rice, and finer group 
distinctions were brought out on this medium than on any other used in 
the cultural studies, but the colors were very mixed and they seemed not 
to stay true to group. Very little reliance was put on these results at 
the time the notes were taken. It is interesting to look back and see 
how nearly true to group the color determinations were. However, the 
mixture of colors produced was so difficult to describe that except for 
grouping purposes it is doubtful if rice as a cultural medium would have 
any specific value. 
