DorAN: ON THE GERMINATION OF FUNGOUS SPORES 325 
as great, that of the urediniospores is 74 per cent as great, that 
of the teliospores is 64 per cent as great, and the range of the 
aeciospores is only 48 per cent. 
IG. I shows the ranges and the cardinal temperatures for 
- these groups, and their -relative positions. 
The results obtained by the writer and others indicate that any 
departure from optimal conditions tends to narrow the tempera- 
ture limits within which fungous spores will germinate. The 
literature contains a very few references to the relation which 
PER CENT 
GERMINATION 
DEGREES CENTIGRADE 
er Soke 6.7.8 940 12 13 14 15 16 1718 19 20 21 22 23 24 25 26 27 2629 30 Ht 32, 
Fic. 2. Curve showing singel limits for the germination of the 
conidia of Venturia inae 
exists between the temperatures required for the process of spore 
germination and the other environmental conditions prevailing 
during that period. Gardner (30) found that the minimum 
temperature for the germination of the spores of Colletotrichum 
lagenarium is 7° C. when the spores are in exposed drops of water, 
but it is 14° C. when the spores are in hanging drops of water. 
When these spores are in exposed drops of prune decoction, the 
minimum temperature for their germination is 4° C. It would 
appear that the presence of nutrient substance and the availa- 
bility of sufficient we hci both tend to lower the minimum 
temperature. 
- The work of the writer included the determination of the 
cardinal temperatures for the germination of the conidia of 
Venturia inaequalis, the spores of Botrytis cinerea, and those of 
