98 



FUXGI AXD FUNGICIDES 



is killed the purple color of the margin changes to 

 brown. The purple spots also appear on the stems of 

 the lower leayes^ gradually extending outward^ until the 

 whole leaf stem may be affected. Minute purplish dofcs 

 are also to be found upon the leaves themselyes^ indicating 

 that the fungus is developing there. In the center of 

 many of the spots oue may often see little raised patches 

 consisting of the spores. 



Of the effect of raspberry anthracnose, Miss Freda 

 Detmers says: ^^The disease is not fatal the first sea- 

 son^ nor does it seem visibly to effect the growth of the 

 young canes ; but the next season, when last year's 

 young canes bear fruit, its destructiveness becomes but 

 too apparent (Plate I, Frontispiece). The effects of the 

 fungus are most noticeable at the time of the ripening 

 of the berries, which do not attain to a normal size, but 

 shrivel, and finally dry up ; the leaves are much smaller 

 than healthy ones, and have a generally unhealthy ap- 

 pearance, later turning yellow, then brown. The canes 

 finally become blackened and die.'' 



The mycelium, or vegetative portion, of the rasp- 

 berry anthracnose consists of slender, microscopic threads 

 which penetrate between the cells of the plant, and 

 absorb their nourishment; the cells thus robbed become 

 first discolored, and then they shrivel and dry up, the 

 tissues finally becoming dead. Toward the center of 

 this dying tissue the mycelium threads unite to form a 

 mass of slender club-shaped bodies {iasidia), w^iich 

 push outward on the thin bark cuticle, or skin, until 

 the latter is ruptured. On the end of each of these 

 club-shaped bodies there is produced a single spore 

 {conidhim). Both the club-shaped bodies and the spores 

 are at first enveloped in a yellowish, gelatinous covering, 

 which, however, is soluble in water, so that during the 

 first rainfall it dissolves and the spores escape. The 

 shape of the spores is represented in Plate XI ; they 



