34« 
Journal of Agricultural Research 
Vol. II, No. s 
parasite (as in culms O2, O3, Pi, P5, P6, and P7), though usually remain¬ 
ing sterile. Thus, the plant is seen to have been infected only in such 
of the buds as were developed from a definite section of the original 
meristem. The few irregularities (culms G2, Hi, Ki, O2, and P6) can 
not be said necessarily to conflict with this interpretation, but were 
probably the result of unusual developments, such as a double infection, 
or, perhaps, of errors in technique or records in repeatedly handling 
these 300 or more buds. It seems certain that the dominance of cases 
showing regularity of infection can not be due to error. 
Plate XXXVII illustrates the appearance of the hyphae in two of these 
nodal buds. The two buds in question are marked by a cross in text 
figure 1. In Plate XXXVII, figure 1, the host tissue was stained more 
deeply than in the other, and the hyphae, which are intercellular, do 
not show as well, particularly those not exactly in focus. Text figure 2 
will assist in locating such as are discernible in Plate XXXVII. It 
should be noticed that in this section the hyphae are seen mostly in the 
tissues on the left, while in the other nearly all of them are on the right. 
Such an arrangement doubtless occurred in the buds from which such 
infections developed as are shown in culms A2, D4, Ei, Fi, etc. 
It is apparent that no assumption of the occurrence of the primary 
infection at or near the maturity of the host can explain the regularities 
of the infection phenomena usually found in these buds without also 
assuming an improbable spread of the infection in the mature tissues of 
the host. The nodal branches were evidently infected early, when the 
buds formed, if at all. As Brefeld (1895, p. 47, 84) observed in con¬ 
nection with his work on infection with Ustilago cruenta , the sorghum 
plant grows very slowly at first for a period of about four weeks or more. 
It was during this time, then, while the meristem, at least in each culm, 
was confined to a comparatively small compass, that the spread of the 
infection must have proceeded in such a way as to determine its later 
development in these plants. 
LIFE HISTORY OF THE PARASITE 
PREVIOUS WORK 
That the head smut infects its host in the early seedling stage has been 
the general assumption as to its life history, although the results of 
inoculations performed by investigators would seem to have given doubt¬ 
ful support to the idea. Brefeld (1883, p. 94) states that Kuhn, who 
named this parasite, obtained a double, artificial infection with this smut 
and Ustilago cruenta. Passerini (1877, p. 236) says he was able to 
reproduce the head smut on maize, but not on sorghum. W. A. Keller- 
man (1891, p. 98, 101) produced slight infection in greenhouse and 
field experiments by inoculating the seed. Later (1900a, p. 9) 1 he 
l See “literature cited” for notes published in 1898; with K. F. Kellerman in 1899; and with O. E. Jen¬ 
nings, reporting further negative results, in 1902. 
