ANTHRACNOSE OF CUCURBITS. 17 
branch thereof. The appressoria are brown, thick-walled, ovoid to 
spherical cells, in general appearance not unlike the intercalary 
chlamydospores of the mycelium. The analogy between these 
appressoria and chlamydospores is strikingly shown in cases where 
appressoria are formed in series, one apparently budding out to 
form another. The appressorium may taper slightly toward the 
point of attachment of the germ tube and may be flattened on the 
side in contact with the substratum. 
A definite round germ pore is found in the center of the lower side of 
an appressorium from which leaf penetration has occurred. For all 
of the strains studied, the size and shape of the appressoria seem to 
be quite uniform. In a few cases appressoria have been observed 
to increase considerably in size and become two celled. 
CULTURAL CHARACTERS. 
Carsner! has described the cultural characters somewhat at 
length. No effort has been made in this work to compare the growth 
on different media. For general purposes a 24 per cent water agar 
containing 2 per cent of dextrose has proved very useful. Besides 
this, potato, bean, and apple-twig agar have been used. The fungus 
erows rapidly and is easily cultured. 
Isolation from diseased specimens was usually accomplished by 
first transferring spores from the acervuli to a drop of sterile water 
on a flamed slide. From this drop loop inoculations were made 
into tubes of melted agar. Plates were poured and transfers made 
from single colonies developing therein. Many of the strains were 
erown from a single spore. 
There is great variation among different strains in the amount of 
aerial growth, the extent of the blackening, and the abundance of 
sporulation. Cultural characteristics tend to change during pro- 
longed propagation, as has been noted in other anthracnose fungi by 
Edgerton (12, p. 393). The strains longest in culture seem to spor- 
ulate most abundantly. Sporulation can be readily secured by the 
use of sterilized segments of cucumber stems. 
In test-tube culture the mycelium is first white or colorless, later 
pink, and finally black. The aerial growth usually becomes pros- 
trate quite promptly. Acervuli appear first as black points and 
sporulation occurs within a week. The pink spore masses may be 
formed for several weeks. In old cultures the black sclerotial 
bodies are prominent on the surface and also scattered through the 
medium to some depth. General blackening of the mycelium may 
extend to some depth also. 
1Carsner, EK. Op. cit. 
69806°—18— Bull. 727-3 
