1036 
Journal of Agricultural Research 
Vol. XXX, No. 11 
sands of oogonia with antheridia and 
oospores, were found in all stages of 
development, the entire apparatus 
being readily recognizable as character¬ 
istic of the genus Pythium. The 
softened tissue was everywhere occu¬ 
pied by branching mycelium, the ele¬ 
ments of which showed little evidence 
of definite orientation (fig. 1). At the 
points where the hyphae passed through 
the cell walls they were constricted to 
approximately half their normal diam¬ 
eter. 
Pure cultures of the fungus were 
readily obtained by placing pieces of 
diseased tissue on corn-meal agar 
plates, and transferring portions of 
SOME MORPHOLOGICAL FEATURES 
Zoosporangia of the fungus from 
cucumber fruits are readily obtained 
by putting pieces of invaded cucumber 
tissue (watermelon or squash tissue 
occupied by the parasite serve equally 
well), or thin slices from the surface 
of Lima-bean agar cultures, into a 
shallow layer of sterile water, which 
should preferably be renewed several 
times to wash away soluble staling 
products and excessive food materials. 
In the course of 2 to 5 hours an abun¬ 
dance of new structures are proliferated 
from the surface and periphery of the 
old mycelia, consisting of stout axial 
Fig. 1.—Section of cucumber affected with cottony leak, showing tissue 
occupied by abundance of branching hyphae, and constriction of latter 
where passing through host cell wall. X 250 
mycelium from the margins of the rer 
suiting growth to tubes of sterile media. 
Through the courtesy of J. I. Laur- 
itzen and G. B. Ramsey, transfers of 
the fungus isolated by them from the 
diseased material found in Pittsburgh 
and in Chicago, respectively, were also 
procured. In general appearance the 
cultures thus obtained were practically 
indistinguishable from cultures of the 
damping-off fungus, Pythium debary- 
anum Hesse. A minor but not insig¬ 
nificant difference could usually be 
made out in watching the development 
of the two types of parasites in parallel 
cultures, as under suitable conditions 
the cucumber fungus shows develop¬ 
ment of aerial mycelium in quantity by 
the end of the second day, whereas in 
cultures of the damping-off organism 
such development generally fails to 
ensue until the third day. 
elements bearing swollen digitate and 
short diverticulate branches, these 
branches frequently undergoing close 
successive ramification to yield some¬ 
what involved complexes corresponding 
to the structure discussed by Butler ( 8) 
as “budlike lateral processes.” At 
other times the branches are fewer in 
number and at irregular intervals in 
open racemose arrangemefit. In any 
case, if the entire apparatus is well 
developed a number of septa varying 
from one or several to a dozen are 
inserted, thus bringing about the de¬ 
limitation of a variable number of 
units, each of which may consist, for 
example, of a digitate branch with its 
secondary lobulate branches, or of a 
portion of the axial element with per¬ 
haps one or more diverticulate or 
branching laterals. After pronounced 
vacuolization of the protoplasm usual 
