Millet Smuts and Their Control 
9 
'"’'Smut of the Foxtail millets may be looked upon as distinct from 
that of Panicum millets, altho, in external appearance, the two are 
somewhat alike. The former is generally regarded incapable of pro¬ 
ducing smut in the Panicum varieties, and if this be true, there is no 
danger of the Foxtail millets becoming smutted from association in 
the field with smutted Panicum varieties. Our experimemnts in 1916 
bore out this conclusion, but in 1917 some negative results were ob¬ 
tained. Further study is to be carried out on this question of cross 
inoculation. 
The parasite grows up within the millet, giving no external evi¬ 
dence of its presence until just before heading-time, at which time 
the mycelium enters the developing ovaries and forms therein the 
characteristic masses of spores (Fig. ) which give the plant its 
smutted appearance. 
These spore masses remain enclosed by the bracts or scales of 
the grain usually until the millet is threshed, when they are broken up 
and the spores disseminated to normal grains. Lodgement of spores 
takes place upon or underneath the bracts, where they remain in a 
dormant state until the grain is sown and conditions become favorable 
for their germination and infection of the seedling millet. 
This simpl life cycle occurs alike in the smuts of both Foxtail 
and Panicum varieties. Obviously, any treatment of the seed that can 
effectively destroy the spores lodged upon the surface and yet effect 
no injury so the seed itself will control the smut. 
TIME AND PLACE OF INFECTION 
Seeding infection is here'the most probable, if not the only, type 
of infection. The germ tubes are capable of growing into the germ¬ 
inating seedling only over a short period of time, probably never tak¬ 
ing place after the seedling reaches a height of 3 inches and generally 
about the time the first leaf is pushing out from its protective sheath. 
Spore germination begins by the rupturing of the spore wall, from 
which emerges a stout germ tube (Fig. ). The germ tube either 
penetrates the seedling directly or produces secondary spores (sporidia) 
which later germinate and bring about infection. In either case, the 
germ tubes penetrate the tender tissues and form a much-branched 
* Ustilagro crameri Korn. Sori dark-olivaceous; ovary infection; spores 
very irregular, rotund or oblong-angular, pellucid, 10-12 by 6-9 microns, 
brownish, olivaceous, smooth, sometimes very finely reticulated. 
Usfilago panici-miliacei (Pers.) Wint. Sori black, pulverulent; panicles 
affected, and ovary of flower destroyed; spores globose to ellipsoidal, 9-12 
by 8-10 microns, rarely angular, epispore yellowish-brown, smooth to punc¬ 
tate; promycelium filiform, cylindrical, commonly 3 septate; sporidia lateral 
or terminal, oblong-elliptic to ovoid. 
