Brown. — Studies in the Physiology of Parasitism. VIII. 1 1 3 
thoroughly rinsed in water beforehand to remove any foreign matter from 
the surface.) 
Beans grown in open ..... 13-4, 13-8, 13-8, 17 *6 
Beans forced in hothouse .... 31 -9, 35-6, 44*3, 49-2 
The exosmosis from the forced plants was considerably greater than 
that from those grown in the open, and in the case of both was greater than 
what is typically obtained from petals. Nevertheless these drops, when 
treated according to the method already described, had no appreciable 
effects in stimulating spore germination. They were found to be practically 
identical with distilled water in this respect. 
The behaviour of the leaves in the present experiment as regards 
susceptibility to attack by Botrytis was found to be as follows : 
Beans grown in the open — spores sown in nutrient— attack commencing 
in 22 hours. 
Beans grown in the open— spores sown in water — no attack in seven 
days. 
Beans grown in hot-house — spores sown in nutrient — attack com- 
mencing in 1 6 hours. 
Beans grown in hot-house — spores sown in water — only doubtful attack 
in 7 days. 
When the spores are supplied with extraneous nutrient, attack takes 
place readily in both cases, and it will be noticed that the time for the first 
signs of attack to appear is shorter for forced leaves than for leaves grown 
in the open. This feature is no doubt correlated with greater development 
of the cuticle in the latter case. 
The slight amount of attack of the forced leaves by spores sown in 
water is of no interest, as it was observed that the leaves had markedly 
deteriorated during the long treatment. It can be truly stated that neither 
type of leaf shows any susceptibility to attack when the spores are sown in 
water. The non-susceptibility of these leaves is thus in complete agreement 
with the fact that the substances passing out have no nutrient value for 
Botrytis spores. 
In the examination of some leaves an interesting result was met with, 
viz. that drops which had lain for some time on the surface of the leaf, and 
which were then found to possess a relatively high conductivity, actually 
produced less germination than did the distilled water controls. This 
result has been obtained in some cases with Bean leaves. The following 
table relating to an experiment with leaves of T radescantia discolor illustrates 
this effect : 
C dZffnmlaf. Effect on germination. 
16-4 
26.5 
26-1 
43-i 
50.2 
Very similar to water control. 
Not so good as water control. 
Similar to water control. 
Distinctly less than water control. 
Almost completely inhibited. 
K 
