MORPHOLOGY OF MOLDS 31 



the fertile hyphu* branch from the vegetative hyphae clus- 

 ters of rootlike hold-fasts or rhizoids are produced. 



In the genus Aspcryillus the spores are borne on the ends 

 of club-shaped stalks, called stcriymata (singular, ster- 

 ijjiiut), which are grouped on the enlarged end of the con- 

 idiophore. The spores are green, yellow, orange, brown, or 

 black. Asperyillus iiiyi r is the most common of the black- 

 spored types; Asperyillu* yltiurus, which occurs on grain, 

 silage, canned fruits and vegetables, is the most common 

 green-spored one. 



In the case of the penicillia, the conidiophore branches 

 one or more times, producing a cluster of parallel hypha?, 

 from the end of which a chain of conidia is abstracted. 

 This results in a broom- or brush-like appearance, which 

 vr'm-s the "vims its name of /'/ uirilliinn, from the Latin word 

 for brush. The most common members of the group have 

 green spores. 



The mold spores, like those of the yeasts, are easily killed 

 by moist heat. 



In the case of the bacteria and yeasts, true unicellular 

 organisms, it is necessary for each cell to be in direct contact 

 with the food. In the case of a mass of cells growing on a 

 solid, the nutrients may pass by diffusion through the nia>s 

 of cells not in direct contact with the medium. In the ease 

 of the molds, cells in actual contact with the food may 

 pass the same to other cells not in contact with it. This 

 enables the molds -to invade vessels that are absolutely pro- 

 tected from the bacterial invasion, such as the cultures of 

 the bacteriologist. 



The production of spores in the air, and thus out of con- 

 tact with a moist substratum, enables the spores to be easily 

 carried away from their point of production by air cur- 

 rents. This method of transportation is favored by their 

 lightness. Their ubiquitous distribution on every object is 



