CERCOSPORA 483 



Spots oblong, olive, showing on both surfaces of the leaf ; 

 conidiophores fasciculate, often crooked and nodulose, septate, 

 brown, 100-130 X 12 /*; conidia acrogenous, straight, cylindri- 

 cal, ends rounded, 4-5 septate, not constricted, dark olive- 

 brown, IOO-H5X 14-18 fj-. 



Ravn has given a detailed account of this species. 



Ravn, Kolpin, Zeitschr. Pflanzenkr., n, p. i (1901). 



Helminthosporium avenae (Eidam.) forms numerous narrow, 

 elongated, dry patches on the leaves of oats, and when present 

 in quantity arrests the development of the fruit. 



Ravn has dealt in detail with this species. 



Closely allied to H. teres^ but differs in the conidiophores 

 not being fasciculate, but scattered, 150-200X9-12 /*, septate, 

 brown; conidia cylindrical, brownish, 4-6 septate, 80-100 X 

 15-16 /*. 



Ravn, Kolpin, Zeitschr. Pflanzenkr^ u, p. i (1901). 



CERCOSPORA (FRESEN.) 



Conidiophores clustered, somewhat flaccid, simple or 

 slightly branched, brownish; conidia worm-shaped, multi- 

 septate, subhyaline or coloured. 



Often growing on living leaves, and forming pale, dry 

 spots. 



Shot-hole fungus (Cercospora circumsdssa^ Sacc.) attacks 

 the leaves of the peach, apricot, cherry, almond, nectarine, 

 etc., forming small circular patches that bear conidia on one 

 or both surfaces ; finally the patches become dry and brown 

 and fall out, leaving holes in the leaf. These holes are 

 usually numerous, and suggest the idea of the leaf having 

 been riddled with small shot, hence the name 'shot-hole 

 fungus.' Such diseased leaves fall early in the season, before 

 the formation of the wood has been completed, or a store of 

 reserve food made by the tree, hence the succeeding crop is 

 a failure. In the case of nursery stock being attacked for 

 two or three consecutive seasons, the trees never thoroughly 

 recover, and, properly speaking, should not be sold. The 

 young branches and also the fruit are attacked at times. 



Conidiophores fasciculate, nodulose, brownish ; conidia 

 acicular, narrowed towards the apex, tinged brown, 50 X 

 3*5-4 /* 



