DORAN: ON THE GERMINATION OF FUNGOUS SPORES 335 
only 4 per cent in moist air as compared with 100 per cent 
in water. This means that in nature the relative number 
of spores of these two last named fungi germinating in moist 
air is very small, but undoubtedly sufficient to cause some in- 
fection. The conidia of Sclerotinia fructigena will not germinate 
in moist air but require precipitated moisture. The conidia of 
Peronospora pygmaea were also found to require precipitated 
moisture rather than moist air for their germination. 
Of the spores studied by the writer and mentioned as above in 
the literature, in only five cases can they germinate well when 
their only source of moisture is the atmosphere. Three germinate 
very poorly in moist air. Six germinated only in precipitated 
moisture. The evidence is insufficient to warrant the conclusion 
that any group of fungi characteristically obtain their water for 
germination principally in the form of vapor. When optimum 
conditions for laboratory experiments on spore germination are 
TABLE V 
Effect of moist air as compared with precipitated moisture 
n the germination of fungous spores 
Spore germinating (relative numbers) 
G. clavi- |S. fructi-\P. pyg- 
pes gena 
|V. inae- 
Moisture conditions 
la 4 qualis 
maea 
100 100 
0 oO 
100 
4 
Ina drop of distilled water 
On dry slide in moist chamber 
100 100 
4 
to be obtained, water in the form of precipitated moisture rather 
than water vapor should be supplied. The question of too much 
water is probably closely related with the question of too little 
oxygen. 
SUMMARY 
I. The germination of the following spores was studied; 
conidia of Venturia inaequalis (Cke.) Wint., conidia of Sclerotinia 
fructigena (Pers.) Schrt., spores of Alternaria Solani M.) 
Jones & Grout, spores of Botrytis cinerea Pers., spores of 
Rhizopus nigricans F. de Wal., aeciospores of Gymnosporangium 
clavipes C. & P., and teliospores of Puccinia Malvacearum Mont. 
2. Spores of parasitic fungi germinate better when obtained 
from the living host than when obtained from artificial media. 
