416 A MANUAL OF THE PENICILLIA 



comparatively long conidiophores, 1 mm. in length, bearing compact peni- 

 cilli consisting typically of a terminal verticil of 4-8 metulae. In the pres- 

 ent study numerous strains have been observed which, in general, comply 

 with this description except that the conidiophores are generally shorter. 

 Representative of this species is strain XRRL 2008 received from Prof. 

 W. H. Weston as a culture isolated from optical instruments by Prof. W. G. 

 Hutchinson, Barro Colorado Island, Panama. Forms of this type were 

 not uncommon among the cultures isolated from deteriorating military 

 equipment. 



The presence of a terminal verticil of metulae is strongly suggestive of 

 the Penicillium citrinum series. Typical strains of P. paxilli as considered 

 here, however, differ from P. citrinum in the following particulars: (1) peni- 

 cilli are consistently larger, i.e., composed of a large number of elements, 

 and are more compact ; (2) colonies are looser in texture and conidiophores 

 are coarser, more consistently erect, and are finely roughened ; (3) the colony 

 colors are in darker shades, quickly becoming dull dark green near andover 

 green (R., PI. XLVII) in contrast to the lighter blue-green colors of the 

 P. citrinum series which approximate artemisia to lily green (R., PI. 

 XLVII); and (4) representatives of this species do not produce citrinin. 

 Penicillium paxilli, as understood by us, also bears resemblance to P. rais- 

 trickii Smith. It differs from the latter species, however, in producing a 

 greater number of metulae which are more compactly arranged and in its 

 failure to develop sclerotia upon any substratum tested. 



Occurrence and Significance 



Members of the Penicillium brevi-compactum series are apparently widely 

 distributed but not particularly abundant in nature. As previously noted, 

 strains are not infrequently isolated from soil, from decaying fleshy fungi, 

 and from slowly decomposing vegetable products, including cereal grains. 



Alsberg and Black (1913) isolated a strain of Penicillium stoloniferum 

 from moldy Italian maize and obtained from it a new metabolic product, 

 mycophenolic acid, with the empirical formula C17H20O6, deduced from 

 analysis, titration value, and estimated molecular weight. It crystallized 

 as white needles, melted at 140°C., and gave a violet color with FeCh in 

 aqueous solution. J. H. V. Charles (in Clutterbuck, et at., 1932), twenty 

 years later, isolated additional strains from similar material. Grabe (1942) 

 reported P. stoloniferum. to represent one of the molds commonly develop- 

 ing in bread. The infection could easily be carried in from the field. 



The biochemistry of the Penicillium hrevi-compactum series has been 

 carefully investigated by Professor Raistrick and his associates. Clutter- 

 buck, Oxford, Raistrick, and Smith (1932) reported 14 out of the 15 strains 

 tested to produce a mixture of phenolic acids, viz. mycophenolic acid 



