YE: REPORT OF THE BOTANICAL DEPARTMENT OF THE 
melon than on muskmelon. The watermelon vines were less 
resistant and the pycnidia were mature a day or two sooner 
than on muskmelon. The watermelon vines were healthy and 
bearing many but small fruits; however, the vines were rather 
short and slender. Possibly the severity of the attack was in 
some measure due to the rather slight vines. It would per- 
haps be of interest to grow some watermelons in a greenhouse 
with the fungus present, for it seems probable that they would 
be naturally parasitized by this fungus. 
Inoculation of cucumber vines.—On August 31, both types 
of mycelia were used to inoculate some nature but still vigorous 
cucumber vines. Three pycnidiosporic and five ascosporic in- 
oculations were made, also two checks for each group. The 
method was the usual one; tangential cuts were made with a 
sterile scalpel into the cortex of the vines, and bits of mycelium 
inserted and covered with grafting wax. 
September 5 there was no change either on the infected or 
the check vines. September 14 some of the wax coverings were 
removed and found to have the cortex of the vines uninjured 
by the introduced fungus. A normal callus had formed over the 
wound. All inoculated bits: of vines were examined micro- 
scopically and cultures were tried from the interior but neither 
method revealed a fungus. 
Why is the cucumber vine immune ?—Since the cucumber and 
muskmelon are species of the same genus (Cwewmis) it was to 
be expected that the cucumber would also be parasitized. As 
there were no younger cucumber plants accessible, their resist- 
ance could not be tested. It seems very strange that this species 
of Cucumis should be immune while a species of a related genus 
is very susceptible. The similarity of stem structure of Cu- 
cumis Melo and Cucumis sativus is evidence that the difference 
in the susceptibility of the two species is not due to their struc- 
tural differences but rather to differences in the cell sap or 
cell constituents.*? . 
%t Parasites, of course, differ in their reactions to the same groups of host 
species, as shown by G. M. Reed’s work, Infection experiments with the 
mildew on Cucurbits, Erysiphe cichoracearum DC. Trans. Wis. Acad. Se., | 
Arts, and Letters 15: 527-47 (1907), Madison, Wis. 
