390 A MANUAL OF THE PENICILLIA 



normal culture by deliberate strain selection. Fruiting structures in such 

 forms generally remain unchanged. 



Saccardo's specimen in Fungi italici, No. 894, \yas examined by Thom 

 and is near enough to type material to establish the identity of Saccardo's 

 species with certainty. A strain was collected in Hanover, Germany by 

 Thom and verified by Professor C. Wehmer as representing the latter 's 

 Penicillium olivaceum, hence synonymous with P. digitatum. Other cul- 

 tures examined have been contributed by numerous investigators in this 

 country and abroad. There seems to be no question but that this species, 

 along with P. italicum, can be obtained from oranges, lemons, etc., wherever 

 these citrus fruits are grown, handled, or consumed. 



A considerable number of species and varieties, undoubtedly synonymous 

 with Penicillium digitatum Sacc, have been described. Of these, only 

 P. olivaceum Wehmer is cited in the literature commonly enough to warrant 

 special comment; others are considered only in the species index. 



Penicillium olivaceum Wehmer, in Beitr. z. Kentn. Einh. Pilze, II, pp. 73-76; 

 Taf. I. fig. 2, Taf. II, fig. 11-15; Jena. 1895. Thom, The Penicillia, p. 245. 1930. 

 Wehmer's description and figures of this species are good and his name for it is so apt 

 and descriptive that it is unfortunate that it must be replaced by that given by Sac- 

 cardo which was considered and refused by Wehmer for members of this group. Our 

 conception of the species was obtained from cultures made directly from rotting 

 oranges in Wehmer's laboratory and compared to specimens actually distributed by 

 Saccardo, thus leaving no room for doubt as to identity. Wehmer's species is synon- 

 ymous with P. digitatxim Saccardo. 



Penicilliiim digitatum Saccardo var. calif ornicum. Thom, in The Penicillia, 



p. 245. 1930 



This variety was based upon a strain which produced white conidia and 

 an entire absence of green color. It was received in May 1924, from H. S. 

 Fawcett, Riverside, California who reported it to be equally as destructive 

 of oranges as the usual olive green form. The strain was soon lost from 

 Thorn's Collection and has not again been reported. The occurrence of 

 white or tan variants has been observed in many species, and the strain 

 upon which Thom based his variety was undoubtedly of such origin. 



Penicillium niveum Sopp (Monogr. pp. 182-184, Taf. XXIII, fig. 16. 1912; Thom, 

 The Penicillia, p. 242. 1930) was compared with P. digitatum Sacc. by Sopp, but 

 close relationship is doubtful. Colonies were described as white with penicillate 

 conidial structures, long tapering sterigmata, and abundant conidia 9 to 18 to 20m. 

 The species might possibly have represented some form approximating P. digitatum 

 Sacc. var. californicum Thom. 



Occurrence and Significance 



Penicillium digitatum Sacc. has been widely studied because of the de- 

 structive olive-green rot of citrus fruits produced by it. As one would ex- 



