328 
placing either spores or mycelium on previously wounded 
surfaces. 
In the ‘‘die-back’’ diseases of woody plants caused by 
germ tubes almost certainly enter through injured buds, while 
in the ‘‘ die-back’ 
rough some injury caused probably in transplanting. 
In the present specimen of Aesculus Pavia the distribution of 
the Botrytis pustules, the youngest being at the upper and lower 
“Sarg regions and the mature ones being in the centre (Pl. vu. 
ig. 1, a) indicates that the primary infection occurred approxi- 
mately in the middle of the diseased region, and would therefore 
take place about twenty-six centimetres above the surface of the 
soil. This eliminates the possibility that the attack was a direct 
invasion of the tree by saprophytic mycelium from the soil as 
in the limes and larches noted above, and postulates a spore 
infection. The brief consideration of the biology of spore infec- 
tion, however, has shown the great improbability of the penetra- 
tion of an unwounded bark surface by a germinating conidium ; 
but although a thorough inspection of the diseased area’ was 
made no wound could be detected. Nevertheless it is almost 
certain that a minute wound must have been present, and it 
would seem probable therefore that infection of the Aesculus 
Pavia occurred by a Botrytis spore, which chanced to be in- 
serted under favourable weather conditions in this very minute 
wound in the bark of the tree—a combination of circumstances 
rarely to be repeated. 
and manner of behaviour. When cultures of Botrytts from 
* Brierley, W. B., loc. cit. 
+ s, F. T., and Bartlett, A. W., loc. cit. 
t Smith, R. E., loc. cit. 
