49 8 



DISEASES OF CULTIVATED PLANTS 



Auricula leaf blotch, caused by Heterosporium auriculi 

 (Mass.), a species remarkable for its very long, slender, often 

 branched sporophores. The spores are not much wider than 

 the sporophores, variable in length, 14-20 X 5-6 /*, often one- 

 septate, steel-grey with an olive tinge. Three or four large 

 olive-green patches are present on a leaf, and as a rule all the 



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; 



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FlG. 150. Heterosporium echinulatum. 1, portion ol a 

 db' ination; 2, cluster of conidiophores bearing 



coniiiia ; 3, conidium germinating, and producing secondary 

 spores. Figs. 2 and 3 highly ra 



leaves of a plant arc attacked, owing to the spores being 

 washed from one leaf to another. When the fungus is 

 mature the tissue of the injured spots becomes brown, and 

 often crumbles away Laving a hole. On cultivated species 

 of Auricula. 



Excess of moisture favours the parasite. Spray with 

 potassium sulphide and ventilate well. 



