142 OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 
erally: in these cases the discoloration gradually works inwardly 
towards the petiole, the dead parenchyma assuming a dirty yel- 
low or light brown color; in other leaves again the diseased 
tissues form sinuate intervenar bands extending from the petiole 
to the edge of the blade. The hairs of tomentose varieties are 
tufts of powdery mildew to have sometimes been taken for them. 
In some instances the leaves show small, more or less brownish 
Брега. я 
Іп severe cases Sun-scald gradates into Folletage. 
Brunissure.—" Тһе disease first appears on the upper sur- 
face of the leaves in the form of very small, very numerous 
yellowish brown spots, in the case of the varieties of the vine 
bearing white fruit, and as brown almost black punctuations, in 
the case of those varieties bearing colored fruit. As these spots 
are all very near one another, for they are separated only by the 
ultimate ramifications of the fibro-vascular bundles, they run 
together almost from the day of their inception. After coa- 
lescence has taken place they form yellowish brown or dark 
brown areas that cover the leaf-blades to a greater or less extent. 
Some cover only the space of half an inch, while others cover 4 
quarter, one-third, the half, and sometimes even the whole of 
the leaf 
“These maculations appear indifferently here and there upon 
the blade of the leaf, now between the veins, now upon the tissues 
adjacent to the veins, and across the latter; now along the edges 
of the leaf, now at the center of the blade. In general they 
form between the veinlets, encroaching upon the main veins and 
the circumjacent tissues later."? 
All the leaves do not become diseased at once. The basal 
leaves are the first to become affected, and the apical leaves, even 
when the shoots have ceased growing, are the last to become 
diseased ; they may even, in mild cases, remain entirely healthy: 
Brunissure has been studied by Viala and Sauvageau, Debray, 
Prunet, Ducomet, and Ravaz. 
Viala describes the appearance of diseased cells as follows: 
ene D We 3 
Bee: P. Les maladies de la vigne, 470 et seq. 1893 Ге. 31. [Translation 
Ravaz, L. La Brunissure de la vigne. Ann. École Nat. Agric. Mon m. 
II. 3: 175 et seg. 1904. [Translation.] 
