DISEASES OF PLANTS. 643 



longitudinal rows, reddish, brown, or black, often slightly depressed 

 at summit, smooth or roughened, most numerous toward the base of the 

 branches. Tlie spots are reddish, brown, or black, often somewhat 

 prominent or sometimes sunken, irregular in size and shai^e. They 

 often split and become somewhat incrusted. Their distribution is very 

 variable over the branches. At length by their cracking and thickening 

 these spots destroy the adjacent cortex. Sometimes by their nbun- 

 dauce and s[)litting the cavities reach down to the pith. On the upper 

 l)ortions of the branches the fungus accomi)lishes the defoliation and 

 desiccation of the vine. 



The leaves present varying appearances. Sometimes the blade 

 becomes more or less red or yellow. Later it becomes dried, the desic- 

 cation appearing at the ijerii^hery of the leaf or between the principal 

 veins. At other times the green color persists with a .slightly paler 

 color between the veins, or at tiie circumference, drying up almost 

 immediately, or after the appearance of red, brown, or yellow irregular 

 si)ots which may sometimes cover the entire leaf. Another aspect of 

 the diseased leaves is the appearance in the green tissue of small, red, 

 brown, or black spots, round or irregular, which by their great num- 

 ber become fused together, drying up the leaf. In addition to these 

 detailed aspects there may be various combinations of them. The 

 spots usually appear on the upper and extend to the lower surface of 

 the leaf, although this order may be reversed. The punctures and 

 spots accompanied by the roughening or slitting may be expected to 

 appear on the petiole and principal veins the same as on the branches. 

 Sometimes the leaves retain their normal size, or are but slightly 

 reduced, are thickened in spots of greater or less extent, and finally fall. 

 Often after defoliation the tips of the branches may also become 

 detached from the vine. 



Spots and elevations similar to those seen on leaves and stem may 

 be found on the fruit, producing similar effects and causing even the 

 entire bunch to dry up and fall off. 



Chytridiose is as yet not a very severe disease of the grape, although 

 of a grave character, and it may be recognized by the color, the dry- 

 ing up of the leaves, branches, and fruit, and the punctures which 

 appear most abundantly at the base of the shoots while still green and 

 on the fruiting pedicels. 



In a later number of the same journaP the author contributes some 

 additional facts relating to the biology of this fungus. During the 

 winter the spores become encysted and upon their emergence give out 

 numerous zoospores, which after germination enter the living wood of 

 the stock, the mycelium penetrating it. Toward the end of the season 

 zoospores and mycelium are rarely seen, but cysts appear to complete 

 the life cycle. This fungus is a true parasite and does not develop in 



1 Compt. Reud., 119 (1894), No. 26, p. 1233. 

 13788— No. 7 5 



