July r5, 1914 
Fusarium on Sweet Potato 
263 
layers in maturity. Two-celled chlamydospores, often produced among 
unicellular ones, are the first indication of a higher development. Irreg¬ 
ular, formless clusters consisting of many chlamydospores are still higher 
in rank, and the highest type seems to be that cluster distinguished by a 
true spherical form. Such spheres have been produced only in Fusarium 
sclerotium Wollenw. of the section Gibbosum (Wollenweber, 1913c, p. 32), 
and all intermediate stages from the unicellular spore to this blue solid 
body could be observed in pure cultures on steamed wheat heads and 
potato tubers. These bodies are doubtless true sclerotia. Their peri¬ 
pheric layer has large cells of dark-blue color. The central part is almost 
colorless and of small-celled parenchymatic structure when sclerotia 50 
to 80/i in size are studied in cross section. 
The fact that these sclerotia can be traced back to unicellular chlamy¬ 
dospores proves the close relation of these two resting stages, and the 
unsuccessful attempt to produce a perfect form in this species leads to the 
opinion that sclerotia replace the perfect stage in this species of Busarium. 
There is no basis for the conclusion that these massive bodies might repre¬ 
sent immature perithecia, because Gibberella, Nectria, and Calonectria 
never have such a uniform structure in the center of the perithecia'in 
similar phases of their development. Consequently it may be concluded 
that the section Gibbosum has species with chlamydospores, such as 
F. gibbosum , F. falcatum, and F. caudatum , and other species with sclero¬ 
tia besides chlamydospores, such as F. sclerotium , but none with a known 
perfect stage. While the section Discolor has species with chlamydo¬ 
spores, it has none with sclerotia and none with a known perfect stage. 
5. Fusarium caudatum, var. volutum, n. var. (PI. XVI, fig. P). 
Diagnosis.—Conidia 3- to 5-septate, averaging 25 to 50 by 2.5 to 4/z in size. Conidia 
more curved, smaller, and with fewer septa than Fusarium caudatum, but agreeing in 
all other characters. 
Habitat.—On partly decayed stored sweet potatoes (Ipomoea batatas), La Fayette, 
Ind. (Collected by Harter and Field). 
D. SECTION ELEGANS 
[Spedes in this section are F. oxysporum Schlecht., F. hyperoxysporum , n. sp.; F. irackeiphilum Smith; 
F. vasmfectum Atk.; F, lycopersici Sacc.; F. niveum Smith; F. redolens Wollenw.; F. orthoceras App. and 
Wollenw.; F. orthoceras, ^ar. triseptatum, n. var.; F. bataiatis, it. sp.; and F. conglulinans Wollenw.] 
6. Fusarium orthoceras App. and Wollenw. 
Fusarium orthoceras App. and Wollenw., 1910, tn Arb. Biol. Anst. f. Land- u. Forstw., Bd. 8, Heft 1, 
p. 1-207,10fig., 3 pi. 
Fusarium orthoceras App. and Wollenw., Wollenweber, 1913, in Phytopathology, v. 3, no. 1, p. 30. 
Diagnosis.—Conidia as a rule unicellular, averaging 5 to 12 by 2.5 to 3.5/1, embedded 
in a cottony mycelium layer, often jellied with age. No sporodochia, no pionnotes, 
and no sclerotia. A few, not exceeding 15 per cent, of the conidia, averaging 25 to 
46 by 3 to 4/i, may be 3-septate. Septal zone nearly cylindrical, slightly curved at 
the apical end, which is unequilateral-conical; the base is nearly straight-conical 
and may or may not end in a very reduced foot; 4- and 5-septate conidia rare, averag¬ 
ing up to 50 by 4.0J u; conidiophore with irregularly arranged sterigmata, seldom tri- 
