124 OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 
The various other stains or reagents that I have used were 
prepared for the most part after the formulae given in Zimmer- 
mann’s Botanical Microtechnique. 
Lraves.—From the description I have given of the appearance 
of diseased foliage it will be seen, upon close examination, that 
leaves have always one or another characteristic in common, and 
may be classified in two groups: first, those leaves in which the 
maculations and striations occur in a field of green ; and secondly, 
those leaves in which the spots and stripes occur in a field of 
yellow. The young leaves that betray a diseased state only by 
the convexity of their blade and a pale color naturally belong to 
the second group, chlorosis being the characteristic of it. 
This separation of the diseased leaves into two groups, while 
of little value for descriptive purposes, and I made no use of it, 
is of considerable assistance in their microscopic examination. I 
found, as would be supposed, that corresponding to the observed 
macroscopic differences, there existed microscopic differences. 
These latter differences, though less pronounced perhaps than the 
former, and more of degree than of kind, appear to best advan- 
tage and in their truer value when considered separately from 
one another. I have, therefore, considered in (a) the anatomy 
of those leaves possessing diseased areas and healthy areas; 
and in (b) the anatomy of those leaves that are entirely 
pathognomonic. 
(а) If one cuts a cross-section through a leaf, being careful to 
include tissue in various stages of disease, it will present, under 
the microscope, very nearly the following appearance: 
The epidermal cells (of upper surface and lower surface also, 
but to a markedly less degree in the latter) are full of matter 
in the diseased areas which becomes less dense and gradually 
disappears as one enters the healthier tissues. This matter may 
be globoidal, homogeneous, or coarsely or finely granular. CR LATE 
3, FIGURE 4; PLATE 4, FIGURES 3, 4, 5.) Тһе globoidal form 15 
infrequent, homogeneity the rule; and both forms do not 89 
beyond the areas of marked disease. When the globoidal form 
is present it may pass over into the homogeneous, or disappear 
as the healthy tissue is approached. The homogeneous deposit, 
