ASYMMETRICA-FASCICULATA 



525 



to recognize the identity of his P. olivaceum with P. digitatum, which had 

 been described from oranges and distributed in exsiccati by Saccardo in 

 1881. 



Penicillium italicurn normally shows some fasciculation of conidiophores 

 whereas colonies of P. digitatum, although loose in texture, remain essen- 

 tially velvety. Penicillium italicnm normally produces larger, more com- 

 plexly branched penicilli in which the constituent elements — i.e., branches, 

 metulae, sterigmata, and conidia — -are generall}^ smaller than in P. digi- 

 tatum. Penicillium italicurn, although somewhat restricted, typically 

 grows more rapidly than P. digitatum on Czapek and other synthetic agar 



Fig. 134. Lemon infected with Penicillium italicurn Wehmer showing the tj-pe of 

 rot characteristically produced. (Photo by Bureau of Plant Industry, Soils, and 

 Agricultural Engineering, U. S. Department of Agriculture.) 



media but not upon such natural substrata as malt extract agar. Peni- 

 cillium italicurn produces conidia in pale gray-green or blue-green shades 

 in contrast to the pronounced yellow-green to olive-green conidia of P. digi- 

 tatum. Parallel with these differences, there are certain similarities which 

 should be noted and which may indica;te a closer relationship between these 

 species than suggested by their placement in the present Manual. Both 

 species produce very irregular penicilli, particularily P. digitatum; both 

 produce strongly elliptical spores, often without showing clear differentia- 

 tion between the youngest conidia and the tips of the sterigmata; and 

 finally both produce aromatic odors on most substrata. 



Doubtfully identified strains can usually be assigned to or separated 

 from the Penicilliuyn italicum series by inoculating them into sound citrus 

 fruits (fig. 134). Well-marked areas of rot begin to appear within 2 to 3 



