Chapter XIII 

 BIVERTICILLATA-SYMMETRICA 



Wehmer (1914) and Thorn (1915a and b) each described the symmetri- 

 cally biverticillate type of penicillus as the outstanding common character 

 for a major natural group of Penicilha. Wehmer proposed to call this 

 section of the genus the Verticillatae, without designating it as a subgenus. 

 Thom referred to it as the Penicillium luteum-'purpurogenum group. Bi- 

 ourge (1923) subsequently applied to it the name Biverticillium and called 

 the section a subgenus. Penicillium purpiiogenum Fleroff-StoU was given 

 as the first species and his discussion clearly indicated that the type of 

 structure found in the Luteum-Purpurogenum Group of Thom, or the Ver- 

 ticillatae of Wehmer, represented in a general way Biourge's idea of Biver- 

 ticillium. However, he went on to include P. aurifiuum Biourge (P. 

 citrinum Thom), P. atramentosum Thom, P. fiexuosum Dale {P. urticae 

 Bainier), and P. fellutanum Biourge — species which could not possibly 

 belong with P. purpurogenum. The idea of a subgenus Biverticillium had 

 to be discarded. 



Later, the long lanceolate sterigmata of the "luteum" type of Penicillium 

 was found to represent a more general and more definite character even 

 than the symmetrical biverticillate penicillus. Thom (1930), therefore, 

 proposed this as the principal identifying character of an entire section, 

 which he designated the Biverticillata-Symmetrica in recognition of the 

 typical penicillus pattern. Subsequent investigations have confirmed the 

 merit and usefulness of these distinguishing characters. Series of species 

 in the Velutina and the I>ivaricata with penicilli commonly biverticillate 

 but asymmetrical and lacking the characteristic lanceolate sterigmata are 

 thus readily excluded. 



The conidiophore of this group typically produces a simple terminal, 

 symmetrical whorl, or verticil, of 4 or 5 to several metulae, each of which 

 bears a symmetrical verticil of closely packed sterigmata. The main axis 

 prolonged usually forms the central metula. This prolongation of the 

 main axis occasionally produces a secondary or superimposed verticil of 

 metulae, and less frequently secondary verticils of metulae arise from the 

 tips of other primary metulae. In marked contrast to such rebranched 

 penicilli, monoverticillate or fractional structures are occasionally present 

 in almost all species, and more or less characterize some species and strains 

 which otherwise clearly belong within the Biverticillata-Sj^mmetrica Sec- 

 tion. 



The typical sterigma of the group is a comparatively slender tube with 



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