July is, 1914 
Fusarium on Sweet Potato 
279 
changeable. It may be reduced to a few hyphae or formed as a thallus- 
like layer. On substrata, such as Robinia stems, a sphaerostilbe-like 
stroma may be formed with a colony of perithecia at the top (PI. XV, 
fig. Z>), or a short but compact stroma develops with a single perithecium 
(Pl. XV, fig. G) or a few together. The protuberancelike projections 
on the peridium are often not confined to the collar surrounding the neck 
or the ostiolum. They may develop on any place, especially when 
moisture allows a continuous growth beyond the time of maturity of the 
spores. These projections (PI. XV, figs. D and E) resemble Hypomyces 
ipomoeae , but all stages from a verrucose to a smooth peridium (PI. XV, 
fig. F) can be secured by selection of media and special methods of trans¬ 
fers in connection with various amounts of moisture. A larger stroma 
develops when mycelium is used in starting the culture on a cotton or 
Melilotus stem. But very few colonies of perithecia may appear with 
this method. Conidia and ascospores transferred to the same sub¬ 
stratum will produce more numerous perithecia with less stroma. The 
illustrations in Plate XV, figures D-G, are made from Gibberella, the 
strain isolated from Ipomoea batatas; but the strain isolated from Triti- 
cum (PI. XIV) corresponds in all respects with the sweet potato strain. 
In brief, these pure cultures show constancy in ascospores and conidia, 
but so much variation in the production of stroma and general appear¬ 
ance of perithecia that field material with such differences would be 
easily referred to more than one species, or even genus. 
key to the; species of fusarium described from pure cultures 
GROWN IN DAYLIGHT 
A. SPECIES OP FUSARIUM WITHOUT KNOWN PERFECT FORM 
I. Terminal chlamydospores present. 
a. Conidia cream-colored to brownish white, except in Fusarium coeruleum (Lib.) 
Sacc.; conidia not sharply pointed at the ends; foot and heel of the base reduced 
to a papilla-like appendage. No wine-red color on sterilized, watered rice. 
Section Martiella.(PI. XVI, fig. K) Fusarium radicicola, n. sp. 
b. Conidia ochreous to salmon colored, except in Fusarium redolens Wollenw.; 
conidia with curved apical end constricted like a flask neck and with a pedi¬ 
cellate base, but without a prominent heel. A wine-red color, turning blue 
upon the addition of alkali on sterilized watered rice, except in F. conglu- 
tinans Wollenw. Section Elegans. 
1. Sickle-shaped conidia; slender, about 11 to 13 times longer than broad. 
a. Sporodochia absent, conidia mostly unicellular, 
Fusarium orthoceras App. and Wollenw. 
b . Sporodochia present; 3-septate conidia up to 100 per cent. 
* Blue sclerotial plectenchymata effuse and few on sterilized potato tuber. 
(PI. XVI, fig. N) Fusarium orthoceras , var. triseptatum , n. var. 
** Blue sclerotial plecten chymata small, convex, numerous on sterilized 
potato tuber.(PI. XVI, fig. D) Fusarium batatatis , n. sp. 
2. Sickle-shaped conidia 8-9 times longer than broad. 
a. Pionnotes reduced. Fusarium oxysporum Schlecht. 
b. Pionnotes perfect.(PI. XVI, fig. F) Fusarium hyperoxysporumy n. sp. 
