374 BOTANICAL GAZETTE [MAY 
of normal and diseased material are from the slides prepared by the 
methods above mentioned. The normal tissue was cut from the 
same leaf as the diseased, unless the leaf showed in all parts the 
effect of the parasitism. In this case a leaf close to the diseased 
one was chosen in order to have comparable material. 
Observations 
1. GAYLUSSACIA BACCATA (Wang.) C. Koch.—The cause of 
the disease is not clear. The diseased area is blackest on the upper 
side, and a white deposit is found on the lower surface of the leaf. 
The normal leaf tissue is as follows: (1) a single layer of nearly 
isodiametric cells in the upper epidermis; (2) a single layer of pali- 
sade cells; (3) a rather loose, spongy parenchyma with compara- 
tively large intercellular spaces; and (4) a lower epidermis of cells 
usually somewhat smaller than those of the upper epidermis. The 
plant studied was collected in early summer, and hence the leaves 
were fully formed, but still in a vigorous condition. The location 
of the plant was at the edge of a wooded area, but open, so that the 
leaves received an abundance of light. The leaf cells have a thin 
peripheral lining of protoplasm, in which the chloroplasts and the 
nuclei are imbedded. The cuticle is nearly colorless, and much 
thicker over the upper than over the lower epidermal cells. 
The parasitized leaf shows a number of changes. Just before 
the palisade cells and after the sponge cells begin to collapse, 
they are filled with a uniformly brown-stained material. Previous 
to this they are filled with a granular mass which is stained yellow- 
brown. In both of these stages of degeneration there are neither 
chloroplasts nor nuclei to be seen. At the same time, the upper 
epidermal cells become considerably elongated, and the cuticle is 
light yellow to brown. In the last phase of degeneration the epi- 
dermal cells become completely collapsed, the palisade cells are 
much shrunken, and the sponge cells have practically disappeared, 
while the cell walls are uniformly brown, and the cells empty. 
2. VIOLA cucuLLATA Ait. (?), parasitized by Puccinia Violae 
(Schum.) DC.—The normal leaf tissue of this plant is rather poorly 
differentiated. The epidermal cells are very irregular in shape and 
size, and the cuticle is thin. The mesophyll is composed of a loose 
