152 A MANUAL OF THE PENICILLIA 



because of the conspicuously smooth character of all walls, especially of 

 conidia and ascospores. 



Upon most substrata, and particularly those containing vegetable ex- 

 tracts, the stock strain of Penicillium levitum produces abundant perithecia 

 but very few sterigmatic cells, either grouped as simple penicilli or arising 

 singly from aerial hyphae. Sector variants characterized by increased 

 conidium formation and an absence of perithecia are occasionally observed, 

 and sub-cultures derived from them seem to maintain the characteristics 

 of the sectors. Conidia are produced fairly abundantly and upon some 

 substrata, e.g., 20 per cent sugar-Czapek, the colony surface may assume a 

 light, pale blue-gray tint. While the number of conidia produced in such 

 variant sub-strains is much greater than in the stock, the penicilli produced 

 are not more complex and seldom show clusters of more than 4 or 5 sterig- 

 mata. Measurements of conidia and sterigmatic cells remain unchanged. 



The perithecia of Penicillium levitum are less highly specialized than the 

 initially sclerotioid structures which characterize most other members of 

 the P. javanicum series. Conidial structures also differ from other mem- 

 bers of the series. Whereas 4 or 5 sterigmata may be arranged in a simple 

 verticil, meeting the essential requirement for placement in the genus Peni- 

 cillium, such definite structures are not consistently produced and the total 

 conidial picture is strongly suggestive of the genus Moiiascus. Such rela- 

 tionship is further suggested by the fact that ascus walls break down rather 

 quickly, leaving the spores free within the ripening perithecium. The 

 species is regarded as properly assignal)le in the genus Penicillium but 

 somewhat transitional in the direction of Monascus. 



Perithecia of Penicillium levitum ripen more rapidly than those of other 

 species belonging to the P . javanicum series but apparently follow the same 

 basic pattern of development (fig. 14). The young perithecium rapidly 

 assumes its ultimate size and appears parenchymatous throughout, A 

 mass of fertile tissue soon develops in the central area and asci may appear 

 as early as the 4th or 5th day in contrast to two or more weeks in such 

 species as P. javanicum and P. parviim. The mass of asci and ascospores 

 usually fills the perithecium within two weeks or less and a thin peridium 

 1 or 2 cells thick confines the ascospores at maturity (fig. 42B). The peri- 

 thecium is hardly firm at any stage and is certainly not sclerotioid, but the 

 continuity of parenchyma-like tissue when young, and the presence of a 

 definite continuous wall at maturity unquestionably place it in the P. 

 javanicum series. 



OCCURRENCE AND SIGNIFICANCE 



Members of the Penicillium javanicum series represent soil forms pri- 

 marily, although they may occur iii other substrata including vegetable 



