254 
Journal of Agricultural Research 
Vol. II, No. 4 
length of 45/1 and an average breadth of 7/t, while the Gibberella-Fusarium 
has 3 to 5 septate conidia, the quinqueseptate ones being up to 6 oti long 
and 5.5/j broad, since isolations of both, which have been repeatedly made, 
from different hosts showed a range of variation in the size of conidia in 
different strains of the same fungus. For instance, F. culmorum from 
Irish potato (Solanum tuberosum) attained only an average diameter of 
6/i, and another strain only 6.5/x, instead of 7/t, as in the original strain 
from Irish potato. Strains from sweet potato and wheat often gave a 
smaller maximum. On the other hand, strains of Gibberella-Fusarium 
already studied from wheat, Irish potato seed balls, sweet potato, and 
stalks of maize reach an average maximum of 6/*, though in general not 
exceeding 5.5/1. The septation also varies a little in different strains from 
the same and from different hosts. The facts fully justify skepticism 
as to a separation of F . culmorum and the Gibberella-Fusarium. 
However, a constant difference between the Fusarium culmorum and 
the Gibberella series has been discovered. Chlamydospore clusters, which 
are absolutely wanting in Gibberella, occur in all strains of F . culmorum . 
This means that the ascigerous fungus, having perithecia, has therefore 
no longer any need of chlamydospores and may have lost this stage. If 
the formation of perithecia has been prevented, the effused plectenchyma 
(PL XIV, fig. J) y which also represents the base of the stroma, may 
function as a secondary overwintering stage. F. culmorum, on the con¬ 
trary, is dependent on chlamydospores if the conidia die from unfavorable 
conditions. Finally, the conidial stage itself, generally reduced in Gib¬ 
berella, is highly developed in F. culmorum, forming great masses of 
conidia in sporodochia and in pionnotes. That the conidia of Gibberella 
are less independent than in the other species is evident from the fact 
that earlier or later they join by their anastomosing germ tubes and 
simply serve as a basis for the ascigerous stroma, thus practically losing 
their existence as a conidial stage. In F. culmorum, on the other hand, 
conidia have been found to be perennial and resistant for years, and, 
besides, are able to produce chlamydospores from their cells if they are 
overwatered or exposed to other unfavorable conditions. 
Summarizing these results, it is seen that there is no good reason for 
regarding Fusarium culmorum, a representative of the section Discolor, 
as the conidial stage of Gibberella. Neither can F. subulatum and F. 
metachroum be a stage of this ascomycete, since they have conidia char¬ 
acteristic of the section Roseum (PI. XVI, fig. G). This section is often 
confused with Gibberella, owing to the frequent association of the so- 
called F. roseum Link with Gibberella on grains of cereals, while the true 
Fusarium of Gibberella is comparatively rare in nature because of its 
ready metamorphosis into a stroma. 
If doubts based only on unproved analogical conclusions suggested 
by certain relationships in shape and color of single stages are disregarded 
and the results of pure cultures in comparison with the same organism 
