344 
Journal of Agricultural Research 
VqI. II, No. s 
it does not ferment any of them. Spores, or decidedly sporelike bodies 1 
(PI. XXXIV, fig. 4), are frequently formed in liquid cultures, which then 
show the brown color characteristic of the resting stage. These may 
also be found occasionally in agar cultures. They are usually undersized 
(7.5 to 12 fx) and show only traces of echinulations. Their germination 
has not been observed. In the upper part of the figure (PI. XXXIV, 
fig. 4) are shown some of these artifically grown chlamydospores (on the 
left) with natural spores (on the right) for comparison. Below are 
shown chains of spores and examples of peculiar formations which are 
suggestive of the involution forms in many bacteria. 
FI/ORAL, ALTERATIONS 
A peculiar reaction between this parasite and the host manifests 
itself by a vegetative stimulus to the host, not only in the vegetative 
parts but also in the inflorescence. 
The parasite of head smut does not always develop a sorus on an infected 
culm, but frequently causes a floral sterility (PL XXXV, fig. 1) which 
develops at times into a peculiar proliferation of the panicle (PI. XXXV, 
fig. 2). This phenomenon, in the tassels of maize, has already been 
noted and figured by Hitchcock and Norton (1896, p. 199). In extreme 
cases of this sort in sorghum (PL XXXV, fig. 2) the ovary and stamens 
entirely disappear and the growth takes the form of a complete individua¬ 
tion in the place of each flower; a tiny culm, with leaves, nodes, and 
rudimentary panicle, shoots up from the head almost as if in an effort 
to escape the parasite. The hyphae of the latter were found in one 
instance to have penetrated the tissues of the phyllomorphic or almost 
phytomorphic flower (Pl. XXXVI). They are distinctly shown in the 
illustration as darkly stained threads in the upper part of the panicle 
and in the bud at its base. In some of the parenchymatous tissue the 
nuclei are abnormal and have taken the stain like the hyphae. A number 
of other flowers less strongly proliferated were examined and found to 
contain no hyphae. It may be concluded from this that the change is 
probably caused by alterations in nutrition processes, especially since a 
somewhat similar though less pronounced phyllomorphism has been 
observed in districts where the head smut does not occur, as at Arlington, 
Va. (Kusano, 1911). 
Where the smut occurs commonly, however, this proliferation of the 
inflorescence is very characteristic and furnishes a more ready means of 
distinguishing the infected plants than the presence of the sori them¬ 
selves. Indeed, of 125 plants of Red Amber sorgo examined in three 
different seasons (1910, 1911, and 1912), mostly at Amarillo, only two 
1 Brefeld (1883, p. 158) obtained the spores of TiUetia fritici in artificial culture and Busse (1904, p. 375) 
has done so with another sorghum smut, Ustilago cruenta Kuhn. He did not culture the head smut, doubt - 
less because of the interference of contaminations which he mentions (p. 377). Griiss (1902, p. 219) has 
described spore formation in U. zeae in cultures. Herzberg (189s, p. 7) does not consider them analogous 
to those formed on the host, although he germinated some of them in the case of U. tritid. 
