342 
Journal of Agricultural Research 
Vol. XXIV, No. 4 
related to F. sporotrichioides n. sp. and belong to the section Sporotri- 
chiella; the third species belongs to section Elegans and is closely related 
to F, orthoceras; and the fourth may belong to section Arthrosoriella. 
Sherbakoff does not recognize any of these species but disposes of them 
all in saying: 
^ No technical description, except results of inoculations for potatoes, always nega¬ 
tive, and certain characters of color and of colony growth, is given, and thus a proper 
identification is rendered impracticable. 
Harter and Field (7) from the results of their work on the stemrot of 
the sweet potato concluded, as Appel and Wollenweber (2), that the 
type of inoculum—mycelium or spores—^has a marked influence on the 
culture. They also proved the pathogenicity of Fusarium hyper- 
oxysporum Wr. and F, hatatis Wr. for the sweet potato and obtained 
negative results in their inoculation experiments with F. oxysporum 
Schlecht., F. orthoceras Ap. and Wr., F. caudatum Wr., and F. radicicola 
Wr. on the same host. 
Wollenweber {23) discussing the species of Fusarium occurring on 
sweet potatoes, points out the necessity of agreeing on the criteria by 
which a ‘‘normar' culture may be known, to avoid wide discrepancies in 
describing what is in reality the same species. He describes 11 species of 
Fusarium, two species of Hypomyces and one of Gibberella occurring on 
sweet potatoes. This included all the species of Fusarium then known 
to occur on sweet potatoes. Under each species is given a **diagnosis’" 
or description of the type culture, habitat, and a general discussion of 
its history and relationships. In the case of new species, of which there 
are 6, the relationships are taken up with a great deal of care. 
A descriptive key to all these species is included based upon the char¬ 
acteristics of pure cultures grown in daylight. Regarding the key the 
author makes the following comment: 
This key might have been based entirely upon the morpholo^cal characters and 
curvature of the conidia .but since the color reactions offer a simpler, though less 
trustworthy means of identification, they have been employed. This key, therefore, 
iould be regarded only as an aid in identification, not as a guide to the morphology, 
which has been discussed in the diagnosis and illustrated in detail in the illustrations. 
Sherbakoff {18) realizing the chaotic condition of the genus Fusarium, 
especially those species occurring on potato, conducted a research 
problem to discover on what basis the American species as well as those 
discussed by Wollenweber could best be separated. 
In general, Sherbakoff verified the principles and the results of Appel 
and Wollenweber’s {2) work in Germany. He believed, however, 
disagreeing with Appel and Wollenweber, that there should be a dis¬ 
tinction drawn between microconidia and macroconidia, and that the 
presence or absence of the microconidia may be used in distinguishing 
species. He also disagrees with Appel and Wollenweber in believing that 
species can be distinguished— 
when grown on almost any medium, including artificial media, provided that 
the medium is not extremely poor or rich in food materials, and also provided 
that the moisture supply in the medium is well regulated. 
Sherbakoff found no coremia nor typical pionnotal form of fructification 
as did Appel and Wollenweber. 
The author outlined the scope of the work, discussed the source of 
material and methods of isolation, culture media, effect of light and 
temperature, variability in the species of Fusarium, relative taxonomic 
