382 BOTANICAL GAZETTE [MAY 
would hardly obtain. The epidermal cells over.a diseased region 
are often filled with a yellowish granular deposit. In the diseased 
area the cells of the vascular bundle and of the parenchyma alike 
become filled with a uniform gray plasm, which later breaks up 
into rounded or hexagonal areas as shown in fig. 9. In the latter 
stage of the disease these attain more clearly defined walls. It 
seems evident that these develop eventually into the fungous spores, 
though the material at hand was not quite old enough to show the 
last stage of the transformation into the spores. No mycelium was 
found in the diseased tissue after the formation of the areas men- 
tioned above had begun. It would seem from this that after a 
certain stage in the disease the fun- 
gous mycelium passes into a plastic 
stage within the host cells, and that 
then the plastic mass breaks up into 
spores as previously described. Miss 
‘ Cs KNOWLES (35) states, in her study of 
yum the effect of this same fungus upon 
Fic. 9—One of the outer ele. the corn stem, that the vegetative 
ments of a vein in a leaf of Zea mycelium breaks up into masses of 
—— ee acs —— a — smaller filaments which swell up, 
nes spore oe a cell, except that in many cases, indeed 
in most cases, the filaments lose their 
individual form and are more or less blended in a gelatinous, shape- 
less mass.” This gelatinous mass fills the host cells at least in the 
leaf tissue. 
12. RAPHANUS SATIVUS L., parasitized by Albugo canadensis 
(Pers.) Kuntze.—The fungus was growing on the cotyledons of 
young seedlings which were grown in the greenhouse. There is 
no regular structure to the parenchymatous tissue, as it is all of 
the ordinary sponge type. There is apparently no great hyper- 
trophy or hyperplasy of the tissues. The blisters seem to be 
caused by the formation of the mycelium, conidiophores, and 
conidia just below the epidermis. Few, if any, changes in the cell 
organs are to be seen. The mycelium is found in abundance. 
The effect of this fungus seems to be merely that of starvation of 
the host, not that of poisoning it. 
. 
TN 
~~ 
