125 
The pycnidia of the fungus are formed immediately below 
the epidermis, or at a depth of a few cells, and usually cause 
the latter to split away from the collapsed cortex. (PI. 
- Fig. 9; Pl. VI., Fig. 4.) 
No conidial formation occurs on the host plant, but in old 
dried diseased shoots occasional chlamydospores are found. (PI. 
fey fig. -6.) 
size and appearance they resemble the chlamydospores found in 
artificial culture media. Of six spores tested in lavender extract 
three germinated and these only in ten, thirty and thirty-three 
days respectively. Of six spores digested with gastric juice, 
washed and placed in lavender extract, two germinated, both in 
they are homologous with the chlamydospores found in pure 
The minuteness of the pycnospores precluded the obtaining of 
definite information as to the manner in which they penetrate 
the host plant. It is to be noted, however, that under natural 
conditions the pycnospores are usually found in considerable 
number in or about the stomata, and that artificial infections 
very often appear to centre in a stoma. 
Relation of Spores to Temperature and Desiccation.—A 
number of observations were made on the relation between the 
germinative capacity of the spores of the fungus, and various 
degrees of temperature and desiccation. The results are sum- 
marised in a tabulated form on pages -9. 
hyaline thin-walled spores are very considerably less 
resistant than the brown thick-walled spore forms. oth the 
former, and the majority of the latter, are killed by exposure to 
a temperature of 53° ©. for 17 hours. The hyaline conidia are 
‘Owever, the pyenospores remain in the pycnidia they are con- 
siderably more resistant to low temperatures, and may even 
survive over winter in a germinable condition. 
_ The thick-walled brown conidia and chlamydospores are 
immune to the action of frost, and exposure to such a temperature 
rate results in the curtailment or elimination of their resting 
period, 
Prolonged desiccation rapidly destroys the germinative capacity 
of the cnospores and hyaline conidia, but is almost without 
effect on the thick-walled spore forms. 
