386 A MANUAL OF THE PENICILLIA 



cause a soft rot from which the fruit quickly loses its shape and may become 

 a flattened slimy mass. Observed upon fruit, the two series can generally 

 be easily distinguished ; once isolated and grown in plate cultures, the two 

 are urmiistakable. Members of the two series occasionally occur in mixed 

 infections although one or the other usually predominates sufficiently to 

 determine and characterize the type of resulting decay. 



Cultivated in the laboratory, members of the Penicillium digitatum series 

 are characterized by their sparse growth and limited spore production upon 

 Czapek's solution agar and other comparable synthetic media based upon 

 comparatively pure sugars and inorganic nitrogen sources. They are 

 equally characterized by their luxuriant growth and abundant sporulation 

 upon malt extract and potato-dextrose agars, and upon Czapek's solution 

 agar to which amendments such as steep liquor or yeast extract have been 

 added. Upon enriched media of the latter type colonies spread rapidly, 

 and are essentially plane and velvety. As abundant conidial structures 

 develop, they assume a dull yellow-green to light olive color. Penicilli are 

 typically biverticillate and asymmetric but vary greatly in size and pattern, 

 and in being mounted show a pronounced tendency to break up into the 

 many cellular elements of which they are composed. The preparation of 

 satisfactory mounts is difficult even from very young cultures due to the 

 deciduous character of sterigmata and metulae. 



While a number of species belonging to this general series have been de- 

 scribed by Sopp (1912), Wehmer (1895), and others, the writers do not 

 believe that any of these differ from Saccardo's material and description 

 sufficiently to warrant continued retention as separate species. 



Penicillium digitatum Saccardo, in Mycotheca Italica as No. 986, Her- 

 barium U. S. Dept. Agr.; in Sylloge Fungorum, Vol. IV: 78, 1886; in 

 Fungi Italici, No. 894. Also Thom, U. S. Dept. Agr., Bur. Anim. Ind., 

 Bui. 118, pp. 31-33, fig. 3. 1910; and The Penicillia, pp. 242-245, figs. 

 29 and 30. 1930 



Colonies upon Czapek's solution agar growing restrictedly, attaining a 

 diameter of about 1 cm. in 10 to 14 days at room temperature (fig. 103C), 

 growth very thin, with vegetative mycelium largely submerged and bearing 

 few conidial structures of small dimensions and of irregular pattern, usually 

 consisting of a limited number of sterigmata bearing conidial chains up to 

 150m in length, variously supported by branches and/or metulae of variable 

 dimensions (for description of penicilli, see malt agar below). Withal, 

 colonies present the general aspect of a mold suffering from some type of 

 nutritional deficiency. 



Colonies upon steep agar growing luxuriantly (fig. 103D), spreading, 

 attaining a diameter of 6 to 8 cm. in 10 to 14 days at 24°C., rather loose- 



