i6o 
BASCOMBE BRITT HIGGINS 
then placed in small droplets on the upper surface of the leaves of 
one plant, and on the under surface of the leaves of the other three. 
The former and one of the latter were then covered with bell-jars. 
Two of those with conidia on the under surface of their leaves were 
left in the open air of the greenhouse, but moist absorbent cotton 
was wrapped around the leaves of one plant. 
At the end of ten days the plants were examined, when several 
Cylindrosporium acervuli were found on the two plants under bell- 
jars, a few on the plant whose leaves were wrapped with moist cotton, 
but none on the plant whose leaves were left exposed to the air. 
This showed clearly that the leaves must be kept moist for satis- 
factory infection to occur; so the bell-jar method was used in all later 
inoculations except where otherwise stated. 
In the next series ascospores were used. Ascocarps which had 
matured on leaves placed in a moist chamber March i6 were on April 
4 crushed in a small amount of sterile water which, after being ex- 
amined microscopically and found to contain quantities of ascospores, 
was used for inoculating several plants. When examined 7 days later 
numerous small white specks, which proved to be acervuli of Cylindro- 
sporium, were found on the under side of the leaves. 
On April 16 two more plants were inoculated in the same way 
and at the end of eleven days 45 acervuli were found on their leaves. 
To determine whether conidia produced in the ascocarps also 
served to propagate the fungus, these were used to inoculate some 
plants. The conidia, if leaves are kept moist after the ascospores are 
shed, collect in small white clusters on top of the old ascocarps. 
Several of these clusters were picked up with a needle and distributed 
in drops of water on sterile glass slides. The water was then examined 
under the microscope and found to be apparently free from ascospores 
which can be distinguished by their smaller size and blunt ends. 
The two plants which were then inoculated with these conidia showed 
several acervuli at the end of seven days. 
Because of the difficulty of obtaining any mycelial growth, no pure 
cultures were ever obtained from these apothecial conidia from P. 
avium. They frequently germinated in water and in agar but when 
the germ tubes had reached less than half the length of the spore, 
growth ceased. 
Inoculations with Ascospores. — The ascospores behaved in much 
the same way. Several hundred cultures were made during the spring 
