OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 137 
not distinctly delineated; disorganization of the cell constituents 
proceeds into the green tisue and starch, if present, is nowise 
abundant. 
(b) Examined in cross-section, those leaves in which the 
appearance of the disease is followed by a progressive chlorosis 
of the entire parenchyma differ from those in which it remains 
normal, i. е., Case a., rather in degree of occlusion of the cells 
and degeneration of their chloroplasts than otherwise. 
The deposit in the epidermal cells (upper epidermis almost 
exclusively) is either homogeneous ОГ granular, apparently 
rarely globoidal. It is never very dense, though generally homo- 
geneous in character where the tissue is longest diseased, and 
becomes granular and finally disappears as one proceeds into the 
surrounding chlorotic tissues. 
The deposit in the palisade cells is usually homogeneous and 
thin, or more or less granular, and proceeds well into the healthier 
tissues. Starch is rarely to be found. The chloroplasts are 
largely resorbed—those still remaining being smaller than in 
normal tissue and reticulate—in the surrounding chlorotic tissues, 
and, in the diseased spot itself, form only comparatively small 
plasmodium-like aggregates. (PLATE 4, FIGURE 5.) 
In the lacunose tissue the cells abutting the palisade layer are 
the freest from deposit; they are frequently almost empty. The 
remaining cells do not differ much in appearance from the 
palisade cells; their lumen, however, is freer from deposit. 
The deposit in the cells of the lacunose tissue is either homo- 
geneous or granular. 
Occlusion of the vessels of the smaller veins is not general, 
nor do thylloses appear to occur in the vessels of the main veins. 
I have just described the general microscopic appearance of 
sections cut through diseased leaf tissue. I will now describe in 
detail the anatomy of the pathognomonic tissues with the view 
of determining as far as possible the nature of the catabolic 
processes brought about in them. 
In describing the California vine disease I said that this malady 
may appear spontaneously as it were, от develop more or less 
slowly. This statement applies not only to the individual vine 
but to individual leaves. 
