•278 



USTILAGINEAE. 



the former is the case when nutrition is abundant, as when 

 under artificial cultivation, the latter under less favourable 

 nutrition ; in very unsuitable conditions, the constituent cells 



Fig. 149. — UstiLago maydis. Diseased Maize-heads after removal of enclosing 

 leaves. The heads are beset with smut-boils of all sizes, some niptlired, others 

 stiU unbroken, (v. Tubeuf phot.) 



of the promycelium may each develop directly into hyphae 

 capable of infecting a new host. 



