117 
media. Small bits of diseased tissue were also put di- 
rectly into the tubes, and transfers from these tubes 
soon gave pure cultures. The result of the isolations 
yielded an abundance of saprophytes belonging to As- 
pergillus and Pénicillium. Species of Cladosporium and 
Macrosporium were found in a few instances. A species 
belonging to the genus Fusarium was almost constantly 
present in the cultures, and this fungus attracts the grea- 
test attention. It shows some striking similarities with 
F. avenaceum (Fr.) Sacc., but differs from this species 
in possessing small conidia, and should therefore be re- 
ferred to the widely distributed F. viticola Thiim. It 
grows well on all ordinary media. When it is grown 
on steamed potato stalks 0 — 1 septated »micro conidia» 
are developed in abundance in about ten days (at 17— 
18° C.). When exposed to light the mycelium takes on 
a faint reddish hue. In about 15 days the characteristic 
conidia are found, usually 3, more rarely 4 — 5 septated, 
40 — 63 X 2,5 — 3p. In potato agar to which sugar has 
been added the mycelial growth is especially vigorous. 
The mycelium becomes orange-red in colour, while the 
agar turns deep crimson. A light yellow pea-decoction 
is turned dark brown or almost black in 3 — 4 months. 
The colour characteristics of this species seem to agree 
entirely with those shown by F. avenaceum and F. 
discolor. 
While inoculations with Cladosporium and Macro- 
sporium yielded but negative results, similar experiments 
with F. viticola turned out positive under the conditions 
prevailing. The data on these points have been brought 
together in the tables given in the next chapter, where 
it is shown that our fungus is able to produce a root- 
and foot-disease which generally ends with the wilting 
down of the plants infected. 
Fusarium viticola belongs to the section Roseam, 
while the typical wilt-provokers of the genus belong 
