Apr. 26, 1924 
Leather Rot of Strawberries 
363 
Sexual stage. —The sexual stage was produced in abundance on potato 
dextrose agar, oatmeal agar, and strawberry extract agar 3 at all temperatures 
from 8 to 25° C. and at the higher temperatures frequently within five days after 
the culture was made. It was also found on naturally infested fruits collected 
in the field. 
Observations to date indicate that the antheridia are practically always 
paragynous. (PI. 2, H to M). In old cultures on oatmeal paste a few were seen 
which were plainly amphigynous. The sexual organs frequently arise from the 
same hypha (PI. 2, H, I, K), though they sometimes seem to arise from different 
hyphae (PI. 2, J, L, M). It is possible, however, that such hyphae are merely 
branches having a common origin, which can not be found because the connection 
was broken or the hypae became badly entangled when the mount was made. 
The question is one which deserves further investigation. 
Fig. 4—Graph showing the variation in diameter of oospores 
Oogonia are hyaline, mature oospores faint yellow to sometimes a delicate 
orange. Germinating oospores, one of which is shown in Plate 2, N, have been 
observed a few times in old cultures on oatmeal agar. 
Measurements of 400 oospores made on material from oatmeal agar cultures 
held at room temperatures for 20 days, are given in Table III, and shown graph¬ 
ically in figure 4. 
Sphaero-conidia. —In cultures 4 to 6 months old on potato dextrose agar a 
few bodies have been seen which resemble the sphaero-conidia described and 
figured by Lafferty and Pethybridge (3, p. 37, and PI. 2, fig. 13) for P. cactorum 
and P. fagi. These bodies vary in diameter from 26 to 44 n and average about 
33 n. They have not been seen on diseased berries. 
aThe strawberry extract agar consisted of 1,000 cc., of water, 15 gm. of agar and the expressed juice 
from 2 quarts of ripe strawberries. When titrated it was found to have a reaction of +31, Fuller’s scale. 
