128 



THE FUNGI WHICH CAUSE PLANT DISEASE 



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tents crowds toward the tips of these cells and a basal septum cuts 

 off the ascus proper from the stalk cell, Fig. 88. The spores then 

 form within the ascus. The ascospores may bud either before 



or after extrusion 

 from the ascus, pro- 

 ducing conidia, which 

 may themselves bud 

 indefinitely, producing 

 secondary, tertiary, 

 etc., crops. In this 

 condition the conidia 

 strongly resemble 

 yeast cells. On the 

 host plant ascospores 

 germinate by germ 

 tubes, which are ca- 

 p a b 1 e of infecting 

 proper hosts. No 

 success has rewarded 

 attempts to secure 

 germ tubes from co- 

 nidia. Leaf infection 

 is chiefly external; 

 rarely internal from 

 mycelium perennating 

 in the twigs. It oc- 

 curs when the leaf is 

 very young. Infected 

 leaves are thickened 

 .,„_„, , , and broadened and 



liG. 87. — T. deformans. 5, distributive bypha; , . ._ 



1, vegetative hyphs; 9, sporiferous hyphee. After the tlSSUeS are Stln 



'*"'^' and coriaceous. The 



palisade cells increase in size and number and lose their chloro- 

 phyll. Blistering and reddening of the leaves follows. 



Asci clavate,. 25-40 x 8-11 /i; spores 8, subglobose or oval, 

 3^ ^i. On the peach in Europe, North America, China, Japan, 

 Algeria and South Africa. 



T. pruni (Fcl.) Tul.*' " is found in Europe and North America 



