ASYMMETRICA-FASCICULATA 523 



text because these names have been used commonly, although by no means 

 consistently, to designate apple rotting Penicillia. 



Penicillium italicum Series 

 (Blue Rot of Citrus Fmits) 



Outstanding Characters 



Colonies growing rather restrictedly on Czapek but spreading broadly 

 upon steep and malt agars; showing limited to abundant fasciculation 

 of conidiophores, depending upon the strain and the substratum, and 

 usually becoming more prominent with age; conidial areas tj^pically in 

 pale gray -green shades. 



Conidiophores arising from the substratum or occasionally from superficial 

 hj^phae, commonly aggregated into conspicuous bundles or coremia 

 1 mm. or more in length and often originating well below the agar sur- 

 face, smooth- walled. 



Penicilli asymmetric, irregularly branched, comparatively long, with metu- 

 lae and sterigmata often arising at several levels within the penicillus; 

 conidium bearing tips narrowed, often merging almost imperceptibly 

 into the chains of cylindrical to strongly elliptical conidia. 



Sclerotia observed in occasional isolates, not in most; regularly disappear- 

 ing in continued culture. 



Odor fragrant, suggesting perfume. 



Responsible for the soft "blue-rot" of citrus fruits. 



The series is represented by a single, well marked species, PenicilUum 

 itaUcimi Wehmer. It is rarely fovmd in nature except on citrus fruits 

 where it causes a characteristic soft rot, and where in advanced stages of 

 fruit decay it appears as a bluish green or gray-green mold covering the 

 rind as a velvety or tufted layer of powdery spores. Parallel with the 

 growth of the mold, the tissue of the fruit breaks down largely as a result 

 of the dissolution of the pectic cell wall substance, and a soft and often 

 shapeless mass results. The rot caused by this species is clearly distinct 

 from that caused by P. digitatu7n Saccardo considered earlier (see pp. 385- 

 392). Whereas both types of rot may occur on any of the different kinds 

 of citrus fruits, the P. italicum rot appears to be relatively more abundant 

 on oranges and grapefruit and less abundant on lemons than that produced 

 by P. digitatum. Both species of Penicillium may occur on the same 

 individual fruit. 



Wehmer (1895) was the first to distinguish between the two types of 

 citrus rots caused by Penicillia, and named the responsible pathogens 

 Penicillium italicum and P. olivaceum. He recognized the first as a blue- 

 green species and the latter as an olive-green form. He failed, however, 



