July 15, 1914 
Fusarium on Sweet Potato 
265 
In order to find whether or not one type strain of Fusarium orthoceras , 
var. triseptatum (PL XVI, fig. N) } could be split up into strains with dif¬ 
ferent percentages of unicellular and septate conidia, the writer sepa¬ 
rated 20 conidia from a subculture of a single spore and transferred 
each to a test tube on potato tuber. Some of these conidia were sickle¬ 
shaped and septate, but most of them unicellular. No differences 
could tie observed as to a remarkable increase of 3-septate conidia, nor 
was there a sign of sporodochia. While the exceptional strain exposed 
to the same treatment did not degenerate to a strain with predominantly 
unicellular conidia, it produced sporodochia on stems in contrast to the 
type strain. It seems better, therefore, to separate this strain provi¬ 
sionally from the others as a variety, unless this contradiction is cleared 
up by more advanced culture methods. The name U F. orthoceras , var. 
triseptatum , n. var./’ is therefore proposed. 
Fusarium orthoceras and its variety are provisionally included in the 
section Elegans, although their conidia have no true bottle-shaped 
apical cell and scarcely a pedicellate base. Inoculation experiments 
are needed to ascertain whether or not this fungus is the cause of one 
type of jelly end-rot of potato tubers. In Watsonville, Cal., in October, 
1913, the writer found up to 80 per cent of Burbank potatoes in a large 
acreage affected by this peculiar soft rot, which is quite different from 
that produced by F, coeruleum and other species. Every year speci¬ 
mens with this disease are sent from California, especially from the 
moorland (called “tule district”) of the San Joaquin Valley. In tubers 
with the jelly end-rot F. orthoceras is often, but not always, associated 
with such fungi as F. radicicola , Mycosphaerella solani , Sporotrichhum 
flavissimum Ek., Rhizoctonia, and also with bacteria. It may be repeated 
(Wollenweber, 1913c, p. 30) that F. orthoceras has been sent to the 
writer from various sources in pure culture under the name “F, oxy- 
sporum Schlecht. ” and that F. gibbosum has been sent under the name 
of the latter species. The complete descriptions and illustrations of 
these fungi will help to determine and differentiate them, and future 
inoculation experiments, based on these well-known organisms, will 
succeed in reducing contradictory reports to a minimum. 
The section Elegans plays the most important part in the species of 
Eusarium on sweet potato because it comprises 4 species determined 
out of 16 strains from various sources, isolated and reisolated from 
Ipomoea. When all of them were at the height of growth, the morpho¬ 
logic characters yrere noted and illustrated. Then inoculation experi¬ 
ments, carried out by E. E. Harter and Ethel C. Field, showed that 
strains reisolated from successfully inoculated plants remained as con¬ 
stant as in the old cultures. This has been proved to be so, and the 
considerable time devoted to get these results seems to have been well 
spent. Two years ago, when this study began, it was the opinion of the 
