THE SPECIES OF THE GENUS PENICILLIUM. 341 



of conidia being produced. According to STOLL (I.), the optimum 

 temperature is 25 C., and the minimum 10 C. The liquefaction 

 of the gelatin is effected very slowly, or may be entirely absent 

 (according to the composition). 



Penicillium olivaceum, Wehmer, is said by WEHMER (XXIII.) 

 to occur, like the foregoing species, almost exclusively as a putre- 

 factive organism on southern fruits, the two being sometimes 

 found together. It is 

 also occasionally met 

 with on European 

 fruit, ZSCHOKKE (I.) 

 having found it as 

 the cause of gradual 

 putrefaction on pears. 

 His description, how- 

 ever, might apply to 

 P. luteum, which has 

 also been found on 

 fruit by BEHRENS 

 (IX.). The colour of 

 the vegetation is an 

 olive-green, like that 

 of P. luteum, but 

 brighter, and lacking 

 the yellow granules 

 excreted by the sterile 



hyphse of the latter. The conidiophores are handsome, but 

 scarcely visible to the unassisted eye, so that the herbage 

 does not appear filamentous. The conidiophores (Fig. 181), 

 which measure up to about 200 /x in length, are less regular in 

 structure than those of the preceding three species, there being 

 no well-defined average system of branching. The branches are 

 1-3 in number, each carrying a few (2-3) sterigmata, about 14 

 by 3 p. The conidia are ellipsoidal, like those of P. italicum, 

 but much larger, averaging 6-7 by 4 ^u* though sometimes attain- 

 ing 10 by 6 fi, and joined together in chains which readily fall to 

 pieces, only the younger and much smaller ones (J-J ft) being 

 firmly connected. The conidia are therefore twice as large as 

 those of the preceding species. No fructification has yet been 

 observed. On artificial substrata, the species forms a yellow - 

 green coating of mould. The optimum temperature of growth is 

 23-25 C., the minimum being about 10 C. The liquefactive 

 action on gelatin is very slight. Further particulars and observa- 

 tions on the cultivation of the species are given by STOLL (I.). 



Penicillium brevicaule, Saccardo, observed by SACCAKDO (III.) 

 with other moulds on decayed paper, has been recommended 

 by Gosio (II. and III.) as a reagent for the detection of 

 arsenic, since, when grown in media containing traces of that 



FIG. 181. Pemtcflltnm olivaceum. 



Conidiophores and conidia. Approx. magn, of 1-2, 

 400 ; of 3, 500. (After Wehmer.) 



