OBSERVATION AND DESCRIPTION OF PENICILLIA 



45 



conidia, since these are common throughout the group, and will progress 

 backward toward the main conidiophore (fig. 7): 



Sterigmata 



The differentiated conidium-producing cell, characteristic of Penicil- 

 lium and related genera, is variously named the sterigma (plural, sterig- 



FiG. 9. Two types of coniilial structures, or penicilli, seen in the Asymmetrica. 

 .4, Typical divaric.ite penicillus of Penicillium nigricans (Bain.) Thom, a member of 

 the Divaricata sab-section. X 1200. B, A typical, compact penicillus of P. stoloni- 

 ferum Thom, a member of Velutina sub-section, X 1200. 



mata), conidiiferous cell, basidium, or following Vuillemin (1910) phialis 

 (plural, phialides). Biourge adopted the latter usage as have G. W. 

 Martin and many other mycologists in America. Since the term sterigma 

 has been more widely accepted, it will be used here. The sterigma as it 

 applies to the Penicillia, may be defined as a transformed and highly dif- 

 ferentiated cell with a tubular body of fairly typical length and diameter 

 that is characteristically narrowed to a conidium producing tube, or tip, 

 from which unicellular conidia are cut off successively to form a chain 

 of varying length, depending upon the species and the conditions of cul- 

 ture. The resulting chain is characterized by fully ripe cells at its distal 



