266 



GENERAL BOTANY 



the branches break off and are disseminated by air currents, thus 

 scattering the mold spores widely. The large number of spores 

 produced, and the great resistance of the spores to extremes of 

 temperature and moisture, account in part for the wide distri- 

 bution of Penicillium in nature. 



ASPEEGILLUS 



Aspergillus is another blue-green mold which often occurs 

 with Penicillium in cultures, and differs from it largely in the 

 nature of the spore-bearing hyphse (Fig. 145). These hyphse 



in Aspergillus swell 

 at the end into a 

 large, spherical cell 

 which looks like a 

 young sporangium 

 of Hhizopus. The 

 swollen end cell then 

 buds out into innu- 

 merable short, radiat- 

 ing hyphse, which 

 together form a com- 

 pact head. Each ra- 

 diating hypha then 

 constricts to form 

 a chain of spores, 

 exactly as in Peni- 

 cillium. In other re- 

 spects Aspergillus is scarcely distinguishable from Penicillium and 

 has essentially the same general appearance and biologic history. 

 Both Penicillium and Aspergillus produce gametes which fer- 

 tilize and produce spore fruits. The sexual process in the 

 molds and in many other fungi seems, however, to have become 

 quite subordinate to the asexual spore process, upon which 

 these fungi depend almost entirely for their perpetuation and 

 wide distribution. 



Spores 



FIG. 145, A colony of Aspergillus, showing 

 mycelium and spore clusters 



The lower figures show in detail the method of spore 

 formation. After Conn 



