July 15, 1914 
Fusarium on Sweet Potato 
269 
E. SECTION ROSEUM 
[Species of this section are F. subulatum App. and Wollenw., F. metachroum App. and Wollenw.; F, 
putrefaciens Ostw.; and F. acuminatum Ell. and Ev.] 
11. Fusarium acuminatum Ell. and Ev. 
Fusarium acuminatum EH. and Ev., 1896, in Proc. Acad. Nat. Sci. Phila., 1895, p. 441. 
Fusartum acuminatum Ell. and Ev., Sacc., 1899, Syll. Fung., v. 14, p. 1125-1126. 
Diagnosis.—Conidia, scattered, in sporodochia or in pionnotes, orange in mass. 
Conidia average as follows: 5-septate, 40 to 70 by 3 to 4.5/c; 4-septate (less common), 
30 to 60 by 3 to 4.5^; 3-septate, 20 to 45 by 2.75 to 4.25^. Conidia of o-, 1-, 2-, 6- and 
7-septations are occasionally found. Subnormal small conidia may be mistaken for 
conidia of the section Discolor, but normal sporodochia develop on repeatedly whorl¬ 
like branched conidiophores, giving the characteristic conidia of the section Roseum. 
The conidia show in side view hyperbolic or parabolic curves, in contrast to Fusarium 
metachroum App. and Wollenw., the conidia of which are as a rule more nearly straight. 
Blue globose sclerotia, 50 to 70 p. thick, occur and form a striking contrast to the car¬ 
mine plectenchymatic thallus on starchy media, such as steamed potato tubers. 
Both blue and carmine are basic modifications of the fungus, while yellow (on rice) 
is the acid one, turning blue to purple violet with the addition of an alkali. 
Habitat.—Occurs on partly decayed plants, especially on stems, roots, and tubers, 
also on fruits. Found on Solanum, Ipomoea, Fagus (beech nuts), and Impatiens bah 
samina in the United States of America. 
Conidia of Fusarium acuminatum (PI. XVI, fig. G) have the parabolic 
dorsal and ventral curvature which is characteristic of the section 
Gibbosum, but less pronounced in the section Roseum. Gibbosum, 
however, requires the presence of chlamydospores and the absence of 
carmine mycelium, while this fungus has no chlamydospores but carmine 
mycelium. Therefore, it has to be classed under the section Roseum. 
The mycelium becomes yellow on steamed rice. This acid yellow modi¬ 
fication turns violet with alkali. This fungus is more distributed on 
Solanum than on Ipomoea and has also been found on Impatiens and on 
beech nuts (Fagus) in the United States. Its conidia (PI. XVI, fig. G) 
are more curved and more swollen towards the middle of the septal zone 
than F. metachroum , but a remarkable relationship to the latter can not 
be overlooked. 
The strains from Solanum and from Ipomoea agreed in all respects. 
The diagnosis is derived from a strain isolated from a potato tuber, but 
many isolations of the same fungus are made from potato stems. The 
strains from beech nuts and Impatiens were a little more slender and had 
a whiplike prolonged top cell often resembling that of Fusarium caudatum . 
Ellis and Everhart (1896) described Fusarium acuminatum as follows: 
Sporodochia gregarious, minute, white at first, then flesh-colored. Conidia falcate, 
attenuate-acuminate at each end, 3-5, exceptionally 6 septate, not constricted, arising 
from slightly elongated cells of the proligerous layer, in which respect it differs from 
the usual type of Fusarium. ... 
Saccardo’s translation (1899) of this diagnosis in Sylloge Fungorum is: 
Sporodochiis gregariis, minutis, ex albo cameis; conidiis falcatis, utrinque attenuato- 
acuminatis, 3-5-, rarius 6 septatis, ad septa non constrictis, e cellulis subelongatis 
oriundis. Hab. in caulibus vivis Solani tuberosi, New York, in America boreali. 
