46 



A MANUAL OF THE PENICILLIA 



end and developing cells at its base, and may contain up to several hun- 

 dred conidia. 



The sterigma of most monoverticillate forms, and most of the Asym- 

 metrica as well, is a cylindrical cell with an acute, more or less tapering 

 apex forming a tube roughly half the diameter of the sterigma (fig. UA). 



A 



Fig. 10. Types of conidial structures, or penicilli. Typical biverticillately-sym- 

 metrical penicilli as seen in Penicillium variabile Sopp, X 1200. 



In the Penicillium janthinellum series the sterigma tapers abruptly and 

 produces a conspicuous terminal tube of fairly uniform diameter (fig. 

 IIB). In the Biverticillata-Symmetrica the sterigma is generally smaller 

 in diameter and longer and narrows more slowly (acuminately) at the 

 apex to a smaller and evenly tapered tube — the mature cell being best 

 described as lanceolate (fig. IIC). In Paecilomyces, a genus commonly 

 regarded as closely related to Penicillium, the sterigma typically consists 



