448 A MANUAL or THE PENICILLIA 



hyphae (fig. 115). They range in color from a fairly bright yellow-green 

 characteristic of P. psittacimmi Thorn, through shades of dull gray-green 

 in many isolates of P. tcrrestre Jensen and in P. resticulosum Birk., Raist., 

 and Smith to the dull blue-green shades of P. solitum. Westling. 



Sharp lines of species demarcation do not occur, and there is considerable 

 doubt as to whether all of the forms included should be recognized. A 

 considerable biochemical literature, however, has been built up around the 

 species retained. Furthermore, individual strains can be found which 

 conform quite satisfactorily with the original descriptions and with the 

 treatment given these species by Thorn (1930) and other investigators. 

 For these reasons, Ave believe it is advisable to recognize Penicillium psitta- 

 cinum, P. tcrrestre, P. resticulosum, and P. solitum and to define them in 

 terms which we believe will permit the user to assign members of this series 

 to one or the other of these species with reasonable satisfaction. It is 

 important to realize, however, that the species intergrade completely, and 

 that it will often be very difficult to determine for example, whether a 

 strain belongs with P. solitum or P. terrestre on the one hand, or P. terres- 

 tre or P. psittacimmi on the other. Penicillium resticulosum alone is 

 unique in the dark reddish brown pigmentation produced in colony re- 

 verse. In considering the biochemical or physiological characteristics of 

 any member of the P. terrestre series, it is believed preferable to regard such 

 a strain as a representative of an abundant and variable series, possessing 

 many characteristics in common, rather than as an exact representative of 

 any particular species. 



Penicillium psittacinum Thom, in The Penicilliu, pp. 3G9-370. 1930. 

 Synonym: Penicillium aureum Corda, in Biourge Monogr., La Cellule 

 33: 111-114, Col. PI. I and PI. I, fig. 2. 1923. 



Colonies upon Czapek's solution agar growing fairly rapidly, attaining a 

 diameter of 5 to 6 cm. in 12 to 14 days at 25°C. and forming a tough felt 

 up to 1 mm. deep upon the surface of the agar, azonate to broadly but in- 

 distinctly zonate, and usually radiately wrinkled (fig. 117A), with broad 

 white margin, conidial areas in the growing period showing a striking shade 

 of parrot ("psittacinus") green near malachite green, deep turtle green or 

 fluorite green (Ridgway, PI. XXXII), becoming shades of olive gray in age 

 and overgrown with a thin weft of aerial hyphae in which anastomosing 

 ropes of hyphae are abundant; marginal areas typically show some funi- 

 culose hyphae during the growing period, with limited fasciculation some- 

 times evident in the deeper central areas ; reverse colorless or in pale shades 

 of yellowish orange; little or no exudate produced; odor pronounced, 

 "earthy"; conidiophores with walls slightly roughened, about 4.0m in 

 diameter, arising either as short branches from trailing or ascending hyphae 



