•Oct. 15, 1924 
Geranium Stemrot 
413 
becoming appressed and felted on 
upper half of slant, with more open 
texture toward base; drying down in 
three months to a uniformly compact 
white mat. No marked difference. 
Carrot agar. —Growth prostrate, 
forming a thick gray sodden mat, wet- 
shining, irregularly wrinkled; aerial 
after three weeks, resulting in a uni¬ 
form woolly white mass; later drying 
down to a prostrate deeply wrinkled 
dry mat bearing small floccose areas on 
upper part of slant, with loose cottony 
masses at base (PI. 1, C.) Radiating 
irregular patches visible by transmitted 
light in central part of colony. Differs 
from other three species in absence of 
early aerial growth and in characteristic 
wrinkling. 
String bean agar. —Prostrate dry 
mat deeply wrinkled in center; aerial 
growth after three weeks, forming a 
-closely appressed felted mass, white at 
upper part of slant, becoming sepia 
brown toward center of slant, with loose 
eobwebby hyphse at base; flattening 
down in three months to a thin dry mat, 
with marked wrinkling in center and 
the characteristic patchy appearance 
by transmitted light. 
Potato agar. —Differs from other 
three species in absence of early aerial 
growth and in wrinkling. Prostrate, 
smooth, sodden mat, bearing short 
downy hyphse after 10 days, flattening 
down after three weeks to a gray, wet 
mat, slightly wrinkled at base of slant. 
Potato dextrose agar. —Prostrate 
sodden mat, bearing tufts of loose to 
felty white hyphse; deeply wrinkled in 
center after three weeks, light-grayish 
olive, with cobwebby tufts of aerial 
hyphse scattered over lower half of 
slant; compact, felted tufts on upper 
half. Differs in presence of wrinkling 
from other three species. 
Sugar beet agar. —Compact white 
aerial growth after one week, bearing 
olive-green slimy masses of oospores on 
center of slant; after two weeks, loose 
wooly-white hyphse, partly overgrow¬ 
ing olive-green masses, later flattening 
down to a sodden, wrinkled, gray mat 
with scattered cobwebby hyphse in 
lower part of tube. Characterized by 
presence of olive-green masses. 
Congo red beef peptone agar.— 
Very scanty surface growth, consisting 
of a few widely scattered prostrate 
hyphse; surface of slant becoming dry 
and glossy; abundant submerged 
growth, filling the agar cylinder with 
long closely parallel hyphse; very 
marked combed-silk effect and radi¬ 
ating patches by transmitted light; 
color of medium changed to deep Indian 
purple (15) within two weeks. No 
color change in others. 
Beef infusion peptone agar.—■ 
Thin, sodden gray mat showing char¬ 
acteristic combed-silk effect and radi¬ 
ating areas; no aerial mycelium devel¬ 
oped. Differs in having the combed- 
silk effect. 
Geranium decoction agar.— 
Growth similar to that on beef agar, 
except that the medium is discolored a 
greenish brown several millimeters in 
advance of growth. Growth much 
slower than that of other Pythium 
species. 
Sterilized geranium stem (with 
distilled water in tube).—Blackened in 
three days except part under water; 
scanty aerial growth on surface of stem; 
abundant diffuse growth out into the 
water. No marked difference. 
Potato cylinders. —Thick, sodden 
gray mat, bearing a few small tufts of 
short downy hyphse; slant covered after 
three weeks with compact downy to 
felty white mycelium, becoming loose 
and cottony at base of cylinder. No 
marked difference. 
Sugar-beet cylinders. — Felted 
white mass within two weeks, closely 
appressed, becoming cottony toward 
base; after two months forming a uni¬ 
formly compact dry white mat. Differs 
in extreme compactness of growth 
from each of the others. 
String bean pods (with distilled 
water in tube).—Sodden gray mat 
covering pod, bearing scattered tufts of 
short downy hyphse, which mat down 
after three weeks or persist in spots; 
thick gelatinous mass floating on the 
water in the tube, with many hyphse 
diffusing underneath. No marked dif¬ 
ference. 
Soyka rice. —Abundant white cot¬ 
tony growth, becoming felty and com¬ 
pact after three weeks; no color change 
after three months. Differs in the more 
profuse growth from the three others. 
VIABILITY 
Duplicate tube cultures on various 
media, which had been kept at room 
temperatures (18° C. in winter to 29° 
in summer) for 6 to 16 months, were 
tested for viability in two experiments. 
A sterile decoction of Quaker oats was 
poured into each tube and removed 
after absorption of fluid by the dried 
agar. Melted corn-meal agar, cooled 
down to 38°, was then poured on the 
slants; the tubes were replaced in the 
incubator and examined up to three 
weeks. Transfers from cultures which 
showed growth on the fresh agar were 
made to oatmeal agar and carrot agar 
for identification and comparison with 
similar transfers from a stock culture. 
Results are given in Table I. 
