ASEXUAL REPRODUCTION 



105 



tuber osa, Lentinus cyathus, and Polyporus mylittae ; or 

 conidiophores as in a species of Botrytis, the sclerotia of 

 which are common on the dead stems of umbellifers. 

 When dry, sclerotia are .very hard and compact, but 

 examination shows that the entire substance consists of 







FlG. 34. Sclerotinia sclerotiorum , a sclerotia-forming 

 fungus belonging to the Ascomycetes. i, portion of a 

 chrysanthemum stem containing black sclerotia .of the 

 fungus in the pith cavity ; 2, sclerotium bearing five 

 ascigerous fruiting bodies ; 3, an ascus with spores, by 

 its side is a paraphysis. Figs, i and 2, nat. size ; fig. 3, 

 highly mag. 



densely interwoven hyphae, white in the interior, and 

 covered with a rind of thick-walled brown or blackish 

 isodiametric cells. Sclerotia vary much in size ; those of 

 Collybia tuberosa and species of Typhula rarely exceeding 

 two mm. in diameter, whereas a sclerotium of Polyporus 

 mylittae now in my possession, measures eight inches in 



