1912] REYNOLDS—PARASITIZED LEAF TISSUE 381 
many of the cells, and the occasional enlargement of the nucleus. 
In some cases the palisade tissue has thus been affected, while the 
sponge cells are less noticeably changed. 
_ 10. XANTHIUM CANADENSE Mill. (?), parasitized by Puccinia 
Xanthii Schu.—The normal leaf tissue is very loosely formed 
between the upper and the lower epidermal layers. The palisade 
is scattered, and the sponge is permeated by very large air chambers. 
Transitional phases between the normal and the diseased conditions 
of the host cells were not found. 
This tissue is more profoundly altered than any other under dis- 
cussion. It is in many places almost completely replaced by the 
fungous mycelium. The cells which remain have no protoplasm 
and are filled with oil globules. On both the upper and the lower 
leaf surfaces the mycelium is abundant and the telial spores are 
very numerous. Within the mixture of parenchyma cells and 
mycelium, which replaces the normal tissue, there are cystlike 
bodies which are composed of masses of mycelium. These objects 
are hollow spheres, and from the inner surface arise telial spores 
exactly similar to those borne in the normal way upon the exterior 
of the leaf. Part of the mycelium near the exterior stained brown, 
while that within the host tissue stained blue with anilin blue. 
11. ZEA Mays L., parasitized by Ustilago Maydis (DC.) Tul.— 
The normal host cells are not changed in general appearance, 
and the general structure of the leaf remains practically normal. 
Very early in the disease the chloroplasts disappear, but the nuclei 
remain until very late in the formation of the spores by the smut. 
In some cases the number of nuclei in a cell is increased, two being 
the largest number noticed. In this condition the nuclei may 
also be slightly reduced in size. The nuclei often become deformed, 
varying from globular to pear-shaped or even crescent-shaped. 
This deformation seems to be due to mechanical forces at least in 
part, for in the first place there are cases in which the nucleus is 
pressed upon on all sides by the forming spores, and the nucleus 
conforms itself to the rounded shape of the spore walls; in the 
second place there are nuclei in the diseased area and even in the 
cells being filled with spores which are normal in shape. If the 
deformation were due to chemic stimulation, this latter condition 
