ASYMMETRICA-VELUTINA 389 



that are typically elliptical but may show wide individual variation ; conidial 

 chains vary greatly in length, up to 150^, usually divergent and commonly 

 becoming entangled with other chains from the same or adjacent penicilli; 

 conidiophores typically very short, commonly ranging from 30 to 100m by 

 4.0 to o.Om, smooth-walled (although granular appearing hyphae are occa- 

 sionally observed under oil), arising from submerged hyphae, or from the 

 basal mycelial felt in colonies upon malt or other nutrient-rich media; peni- 

 cilli typically biverticillate and asymmetrical but varying greatly in dimen- 

 sions and complexity (fig. 102), rarely appearing monoverticillate or un- 

 branched, with branches, metulae, and sterigmata often poorly defined; 

 consisting of branches varying greatly in length and bearing either metulae 

 and sterigmata, or sterigmata only; metulae variable in form and dimen- 

 sions, commonly ranging from 15 to 30m by 4.0 to G.O/i and bearing sterig- 

 mata in variable but always limited numbers; sterigmata equally variable 

 and ranging from 15 to 28iu by 3.5 to 5.0/i, usually producing chains of 

 elliptical conidia, but occasionally terminating in swollen vesicular cells; 

 conidia smooth-walled, dull dark green in mass, varying greatly in form 

 and dimensions (fig. 102), ranging from subglobose to long cylindrical in 

 shape but usually elliptical, commonly 3.5 to 5.0^ by 3.0 to 3.5^ at first, 

 then 6.0 to S.O/x by 4.0 to 6.0^ and occasionally up to 10 to 12/i by 6.0 to S.Ojj. 

 with substantial differences in form and dimensions of conidia commonly 

 occurring within the same chain. 



The above description is based primarily upon NRRL 786 (Thom's No. 

 176), isolated by Thom in 1904 at Storrs, Connecticut, which has been main- 

 tained continuously in laboratory culture since that time and which has 

 been checked against Saccardo's exsiccati, a portion of orange peel, dis- 

 tributed in 1880. The species is represented also by NRRL 1202 and 

 NRRL 1203 isolated in 1940 from a lemon and an orange respectively at the 

 Northern Laboratory, and numerous strains more recently isolated from 

 spoiling citrus fruits in connection with the present study. A culture re- 

 ceived from the Centraalbureau under this name was entirely typical. 



Experience indicates that the description as presented will adequately 

 cover all but an occasional member of this series as they are isolated from 

 fruits collected from packing plants, storage warehouses, and consumer 

 markets in this country and abroad. Occasional variants are encountered. 

 One such form producing Avhite conidia and showing no green color was 

 sent to Thom in 1924 by Dr. H. S, FaAvcett, Riverside, California, and in 

 Thom's JMonograph (1930, p. 245) was cited as a new variety, Penicillium 

 digitatum Sacc. var. californicum. Less striking variants are commonly 

 observed, and forms characterized by more or less restricted (fig. 103F) 

 rather than broadly spreading colonies (fig. 103E), when grown upon malt 

 extract or other nutrient rich media, can be separated from almost any 



