4 i6 
Journal of Agricultural Research 
Vol IX, No. is 
microscopically without definite measurements. Subsequent examina¬ 
tions made with the microscope, from cultures of various ages, as well as 
from a variety of different media, showed this difference constant, the 
diameter of the mycelium of R5 being in every case smaller than that of 
the remaining strains. Measurements of R5 and the remaining strains 
were made from cultures of the same age grown on the same media. 
The procedure followed was to grow the cultures in petri dishes, and 
mounts on slides were made a definite distance from the original plant¬ 
ing. Fifty measurements were made at random in each case. The 
results of these measurements show that the diameter of R5 varies from 
4.7 to 8.8 with 7.8 fx as the average measurement, while the measure¬ 
ments of the remaining strains vary from 10 to 14.0 m, with 10.1 \i as the 
average. Figure 1 illustrates this difference comparatively, both sec¬ 
tions being drawn with the aid of the camera lucida, with the same 
magnification and from cultures of the same age. That the thickness 
of the mycelium is a good 
distinguishing character 
was confirmed as follows: 
19 mounts were made from 
cultures grown on various 
media and of varying ages. 
The R5 was marked at the 
time of mounting, but in 
such a way that the person 
to whom they might be sub- 
Fzg. i.—C amera-hirida drawings of mycelium of the Ri and R$ mitted was Unaware of any 
strains from the same medium and cultures of the same age. . ... « J 
distinguishing marks. 
These were submitted to two pathologists of the Office of Cotton, Truck, 
and Forage-Crop Disease Investigations, with a request that they divide 
the mounts into two lots, based on the diameter of the mycelium. In 
every case the mounts of R5 were separated from the remaining strains. 
Not only is the diameter of the mycelium of R5 smaller, but likewise 
the short sclerotial cells enveloping the sclerotia are smaller, as shown 
in figure 2. One hundred measurements show that those of R5 vary in 
length from 13.6 to 30.6 with an average of 21.6 while the others 
measure 17 to 61.2 with an average of 37.5 In width those of R5 
measure from 8.3 to 20.4/x, with an average of 12.3 m- The other strains 
measure from 11.9 to 23.3 with an average of 16.7 n. Generally they 
are also much more regular than those found in the remaining strains, so 
much so, in fact, that they can be described as ‘‘ monilia-like.” In the case 
of the others, Ri, R2, etc., while occasionally one sees a chain of regular 
sclerotial cells, this is the exception rather than the rule. It may perhaps 
be argued that R5 was contaminated with another sterile fungus the 
mycelium of which resembles that of a species of Rhizocotonia, but is of 
