DISEASES DUE TO FUNGI 85 
shortening of the internodes is more marked at. the top 
of the plant than at the base, presumably because the 
low temperature which prevailed while the lower parts 
were developing kept the fungus in check. The root of 
the plant is affected by Fusarium wilt to a much greater 
degree than is the case with Verticillium wilt, and 
during the last stages of the disease the roots may be 
completely destroyed. Another distinguishing feature 
between this and Verticilliwm wilt is the colour of the 
infected wood inside the plant. In Verticillium wilt the 
light brown colour of the affected wood extends practi- 
cally to the growing point, while in 
Fusarium wilt, the colour usually (\ 
ends at least a foot below, and in a. 
most cases does not extend so far. 0 
The colour of the wood in Fusarium 
wilt is a much darker brown, and in 
the root is almost black. The fungus Os 
passes from the main stem, through 
the leaf traces into the leaves, and Ps 
occasionally reaches the fruit. No 
fungus growth appears outside the c. 
stem until the plant is dead, when 
a pink growth forms round the 
basal parts. A similar outgrowth 
: ais Fic. 18. Spores of Fusarium 
appears in the case of Verticilliwm —easinfectum: = (a)_ micro- 
wilt, but the colour is white at first. itsaeaea 
It is not always possible to distinguish between the two 
diseases in this way, as saprophytic F'usaria often produce 
a pink growth over that of Verticilliwm. 
Causal Organism.—The disease is due to Fusarium 
lycopersict Sacc., which name was first given by Saccardo 
to a fungus he found growing upon decaying tomato 
fruits. The genus Fusarium produces three kinds of 
spores or conidia (Fig. 18). One kind are very small 
microspores, others are larger and sickle-shaped with 
three or four cross walls, while the third type consists 
of thick-walled chlamydospores, or resting spores, 
