SCLEROTIUM DISEASE 



151 



separated Orders. Among others may be enumerated 

 potato, chrysanthemum, hemp, haricot beans, petunias, 

 zinnias, cucumbers, swedes, turnips, etc. The stem is the 

 part most frequently attacked, but, according to Potter, 

 stored swedes and turnips are also destroyed, the disease 

 first showing itself just above the ground-line as a delicate 



The mycelium also 



white mould encircling the stem. 



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% 





\t. 



Fig. 32. — Sclerotinia sclerotiorum. i, portion of a 

 chrysanthemum stem containing the black sclerotia of the 

 fungus, nat. size ; 2, a sclerotium bearing five asco- 

 spores, nat. size ; 3, an ascus with spores, and a 

 paraphysis, x 300. 



penetrates into the interior, and gradually extends upwards. 

 Finally the stem becomes dry and brittle, and falls down. 

 If such diseased and fallen stems are cut open, a considerable 

 number of black sclerotia of very variable size and shape 

 are met with in the pith, surrounded by mycelium. 



When the stems decay, the sclerotia are set free and lie 



