OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 149 
two diseases are in a large measure similar. The importance of 
this similarity is enhanced when the anatomical study of patho- 
gnomonic tissues in the former malady fails to reveal the presence 
of any foreign organisms, but simply shows a chloroplastid de- 
generation inversely proportional to the rapidity of death, and an 
occluding of the cell lumen by a gummous product probably due 
to starch decomposition. When we also consider that Roze 
is credited by Debray! with having found Pseudocommis Vitis 
(Syn. Plasmodiophora Vitis) in leaves taken from vines attacked 
by Folletage it can hardly be denied that the two diseases are very 
closely related, for this supposed organism is the cause of 
Brunissure, which malady I have shown to be undifferentiable 
anatomically from the California vine disease. Furthermore, we 
know that sun-scald may gradate into Folletage and, a fact also 
of capital importance, that this malady is prevalent in southern 
California—the home of the California vine disease. 
The California vine disease, Folletage, Sun-scald, and Brunis- 
sure are then very closely related. In fact, a close and compre- 
hensive study of the anatomical features ef these diseases cannot 
help but lead one to the conclusion that all four are due to the 
some functional state in the vines themselves, outwardly indi- 
cated, owing to the play of external agencies, by somewhat differ- 
ent symptoms. This common functional state I shall call a lower- 
ing of functional activity; and for the following reason: In the 
California vine disease—one might say without grave inaccuracy 
in all four diseases—the anatomical changes observed follow very 
closely those occurring in autumn leaves, preeminently is this the 
case when the sequence of changes is slow. Now it is well 
known that the changes brought about in the leaves of deciduous 
plants in autumn are due to a lowering of functional activity. 
The rest these plants require after a certain period of growth 
takes place normally at the end of such a period, provided condi- 
tions are not conducive to its prolongation, without the determi- 
nant intervention of external agencies. The róle of external 
agencies is largely of secondary importance; they hasten or retard 
autumnal changes in the leaves, but they will not bring them 
'Debray, А. Bull. Soc. Bot. France 45: 256. 1898. 
