[Vor. 3 
52 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
That reaction of different parasites to the temperature rela- 
tions may differ even within a single genus, is well brought 
out in the genus Glomerella. Неге, on the one hand, is found 
Glomerella rufomaculans which is dependent on a maximum 
temperature of 32°C. for the outbreak of an epidemic (Scott, 
06), while on the other, Colletotrichum Lindemuthianum 
(Glomerella Lindemuthianum Shear) is reported by Edgerton 
(715) as being unable to grow in culture above 31°C. Не 
shows that this species causes the most severe injury at cool 
temperatures, infection being inhibited by the summer heat. 
Fungi Imperfecti.—Little has been done as to this relation 
in the Fungi Imperfecti. Ravn (700) has shown that in the 
case of Helminthosporium teres, the attack on barley was con- 
ditioned on cool temperatures at the immediate time of sprout- 
ing of the kernel in the soil. Similar conditions held for the 
stripe disease of barley, caused by Helminthosporium grami- 
neum. By growing the plants under controlled conditions of 
temperature, this author was able to show that a temperature 
of 6.5-14^C. favored the disease, while a temperature of 19- 
25°C. practically excluded it from the seed-beds. He showed 
that the susceptible period for infection was immediately at 
the time of germination of the seedling, and that plants 
sprouted in warm temperatures, which were then immediately 
removed to cool conditions, did not become infected. Bakke 
(12), in Iowa, showed that the optimum for growth of this 
fungus in culture was 23-25^C., so that it would appear that 
the effect of the temperature was one of resistance or escape 
on the part of the host rather than an effect on the fungus. 
Further evidence bears out this belief, since Helminthosporium 
teres can cause a leaf spot in the field at the higher tempera- 
tures. 
The question of the temperature relations of the parasitic 
species of Fusarium will be diseussed later and may be dis- 
missed here with a brief statement that, as a rule, they seem 
to require high temperatures for their most virulent attack. 
In this they appear to be opposed to the closely related genus, 
Verticillium, which also causes wilt diseases (Wollenweber, 
552); 
