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ON A NEW CANK.ER-DISEASE OF PRUNUS Y'EDOENSIS, etc. 
9. Confirmation of the Genetic Relation between Pycno- and 
Ascosporous Stages. 
On the infected area of the branches and trunks, two spore forms, pycno- 
and ascospores, usually develop in different stages, as already described. It 
has been demonstrated by various authors that some species of Cytospora 
belong to Valsa as its pycnidial stages. In my case also, the pycnidial stage 
of the causal fungus is a species of Cytospora. 
Inoculations made with pure cultures of our Valsa and Cytospora produced 
the same results. The characters of pure cultures of these two types of the 
spores are quite identical. As a direct proof, the ascospores of Valsa 
were inoculated on the sterilized twigs of Prunus yedooisis. As I had 
anticipated, a Cytospora was at first produced which is identical in every respect 
with one on the natural host, and finally the Valsa stage was reproduced. 
Moreover, when the Cytospora spores were inoculated on the sterilized twigs 
of the same plant, the same Cytospora was reproduced, and after a long time 
a Valsa form was produced which is identical with the causal fungus. 
10. Drop-Cultures. 
a. Germination of pycnospores. 
The pycnospores were not made to germinate well in pure water. 
Although I sowed the spores in a drop of distilled water over and over again, 
I could not succeed in making them germinate well. But once in a while 
I noticed that a few spores put out a slender germ-tube at one end, without 
conspicuous swelling, but soon died for want of nutrient. I also got the 
same negative results with rain-water, tank-water, and various kinds of sugar 
in such low percentages as i, 2, 5 or io°/ 0 . I have found the most satis- 
factory medium for this purpose to be a decoction made by boiling host-bark 
and diluted pear juice. 
The time required for germination varies with the temperature. At 
room temperature in summer, which ranges from 20 0 to 28°C, the germina- 
tion occurs in thirty to sixty hours. At lower temperatures the process often 
