ASYM.METRICA-DIVARICATA 255 



More detailed characterizations of the different sub-sections are given 

 ill the introductory statements which j^recede consideration of the series 

 and species which comprise them. 



ASYMMETRICA 

 Sub-section: DIVARICATA 



PenicilU are strongly divaricate in most species, and in the majority of 

 forms consist of a terminal group of irregularly arranged branches and/or 

 metulae bearing clusters of sterigmata (fig. 69). These branches are 

 commonh' imicellular and together with the sterigmata borne thereon, 

 present the general appearance of a group of monoverticillate penicilli. 

 The terminal cluster commonly consists of a prolongation of the main axis, 

 or an indehnite number of fertile branches arising irregularh^ at lower 

 levels to comprise a loosely arranged bi^•erticillate and asymmetric peni- 

 cillus. In a limited mmiber of species the fertile branches arise at one 

 general level in the manner of true metulae and comprise fairly compact 

 but definitely divaricate penicilli. Colonies often consist of a rather 

 close-textured and comparativeh' tough basal felt at or near the agar 

 surface, from which a loose-textured and often flocculent overgrowth 

 commonly tlevelops. Most, but not all, species grow rapidly to produce 

 broadly spreading colonies, ^^egetative hvphae are generally thin, deli- 

 cate, and rarely exceed 3.0/i in diameter. Conidiophores may develop 

 directly from the basal felt or arise as bi'anches from aerial hyphae. ^^'alls 

 may be smooth, fineh' granular, or in a few forms conspicuousl}^ roughened. 



Members of the group are always present in cultures made from soil, 

 but may occur also upon vegetable remains and upon other organic mate- 

 rials in the later stages of decomposition. They frequently occur on 

 fabrics and other military eciuipment undergoing deterioration in the field. 

 Some forms are unusually tolerant of and may occur in strong acid solu- 

 tion and in copper and nickel electroplating baths. Others sometimes 

 occur as "bottle imps" in various laboratory reagents. 



The Divaricata are regarded as representing, in the main, a natural 

 group of. Penicillia. However, the group should be considered as occupy- 

 ing a somewhat intermediate position in the genus as a whole, since differ- 

 ent members assigned here show obvious affinities to other well marked 

 groups. 



Members of the Carpenteles (ascosporic) series show a definite relation- 

 ship to the PenicilUum Javanicum sei'ies of the Monoverticillata (see p. 

 132), but are excluded from the latter by the consistent development of 

 l)ranched penicilli. Similarly, members of the P. raistrickii series seem 

 to be closely related to P. thomii and allied species but are separated from 

 them upon the same basis. 



