790 
Journal of Agricultural Research 
Vol. V, No. 17 
potato cylinders and Irish-potato agar the growth has a darker appear¬ 
ance than on oatmeal agar, beef agar, and string-bean agar, owing to the 
fact that the numerous erect conidiophores bearing hyaline spores are 
produced in greater abundance on the three latter media and give a 
grayish appearance to the upper surface. If the conidiophores and 
spores be scraped away, the mass is black beneath. Growth appeared 
only on oatmeal agar at temperatures varying from 30° to 32 0 in 14 
days. From these results it appears that temperatures as low as 6° to 
7 0 and as high as 30° to 32 0 prohibit the normal growth of the fungus. 
The vegetative growth on artificial cultures is hyaline at first and later 
brown (PL TVIII, L), with the exception of the end cell of the conidio- 
phore, which at its outer extremity is hyaline to slightly brown (PI. 
LVIII, A y By L). The conidiophores are branched, septate (PL LVIII, 
Ay L)y and vary in length from 30 to 225/*. The conidia are continuous, 
granular, and hyaline to slightly brown with age (Pl. LVIII, M). As 
soon as one conidium is mature, it separates easily from the conidiophore 
and another begins growth by a swelling of the end cell of the conidio¬ 
phore, to be dropped in turn when mature. This process is repeated as 
long as the environment of the host will permit. It should be noted in 
this connection also that this fungus can be reproduced by hyphse as well 
as from the spores. It is likely also that vegetative reproduction ac¬ 
counts for a larger part of the infections under natural conditions. In 
fact, certain vegetative parts might be confused with or mistaken for 
conidia. Although conidia are not produced in abundance on the host, 
they frequently develop normally on diseased potatoes kept for some 
days in a moist chamber. 
The conidia under laboratory conditions germinate slowly in rice or 
sweet-potato decoction. One or two growths (Pl. LVIII, K) are thrown 
out usually at the end of the conidia, which attain in 24 hours a length 
about equal to that of the spore. The branching of the hyphae begins 
the second day (PL LVIII, N) y and the production of the brown pigment 
in about three days. 
TAXONOMY OF THE FUNGUS 
Halstead attributed the scurf to a new genus and species, Monilochaetes 
infuscansy but he gave no technical description of it that the .writer has 
been able to find. The fungus belongs to the Dematiaceae of the Hypho- 
mycetes. However, the writer has been unable, after considerable 
study of the fungus, to fit it into any of the genera so far described. It 
is, however, desirable, in view of the fact that it is a rather common 
and conspicuous fungus, that it have a description by which it may be 
recognized. The fungus has been known as Monilochaetes infuscans 
and as the cause of the sweet-potato scurf for 25 years. Taubenhaus and 
Manns 1 in a recent publication likewise refer to Monilochaetes infuscans 
1 Taubenhaus, J. J., and Manns, T. If. The diseases of the sweet potato and their control. Del. Agr. 
Exp. Sta. Bui. 109, p. xx. 19x5. 
