176 COMPARATIVE MORPHOLOGY OF FUNGI 



cystis, they branch repeatedly (Fig. 116, 1 and 2). In the only cytologi- 

 cally studied species belonging to this subgenus, the phialides, and hence 

 the conidia, are uninucleate. 



From Aspergillus, Aspergillopsis and Citromyces form an unnotice- 

 able transition to the second important genus whose conidiophores are 

 much branched and lack the capitate swellings at the junction of phia- 



Fig. 110. — Pcnicillium claviforme. Coremia on malt agar, with snowy aerial mycelium. 



(After Wehmer, 1914.) 



lides (Fig. 117, B). The outermost branches from which the phialides 

 radiate have a certain systematic value and are called metulae (Westling, 

 1911). While in the majority of forms the metulae and phialides (like 

 the hyphal cells) have several nuclei, in some strains of the Penicillium 

 crustaceum group, as in Aspergillus (Sterigmatocystis) nidulans, they 

 are uninucleate; in these forms on a thallus with multinucleate cells 

 there arise uninucleate conidia which only at germination again become 

 multinucleate. 



