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as a rule to the section Elegans. Among the species 
discussed in the preceding chapter and known to infect 
peas F. redolens is included in the section Elegans , F. 
avenaceum in the section Eoseum , and F. falcatum in 
the section Gibbosum. Thus we have pea-infecting spe- 
cies belonging to several groups. Now it is of very 
great interest to find that the species belonging to dif- 
ferent sections differ in their way of attacking the host. 
Elegans contains almost exclusively purely vascular para- 
sites, while other sections, such as Eoseum and Gibbosum , 
show a striking contrast to Elegans in being able to 
destroy parenchymal tissue (Wollenweber 4). A compa- 
rative study of the different pea-infecting F mama as 
regards their way of attacking the host would be of 
great interest. That F. viticola and F. avenaceum require 
quite favourable conditions (high humidity) in order to 
be able to destroy parenchymal tissue seems certain. 
F. redolens is sometimes vascular in habit, and F. fal- 
catum , although belonging to the section Gibbosum , is at 
least partly vascular (Schikorra 3). 
The different mode of attack, together with the 
differing degree of pathogenicity in the different species, 
may afford one explanation — and that perhaps the 
simplest — of the seasonal appearance of fusariose in 
peas. The »St. John’s disease» would then, after all, 
comprise a distinct group of Fusarium- diseases appear- 
ing in early summer and caused by virulent Fusaria 
frequently vascular in habit. Both van Hall and Schi- 
korra deal with this type of fusariose, although diffe- 
rent species were involved. That Fusaria belonging to 
other group may also sometines be found together with 
these species — for instance F. avenaceum with F. fal- 
catum as reported by Appel and Wollenweber (1) — 
does not invalidate the distinction made, F. avenaceum 
being in such a case only of secondary importance and 
not involved in the development of the typical disease. 
