PRINCIPAL GROUPS OF PLANTS. 51 



the sensation commonly called the "smell of mold." They are cap- 

 able of germinating on almost everything, as old shoes, old paper, 

 as well as on bread and other articles of the household. They may 

 occur on "moldy drugs," and in pharmaceutical preparations, as 

 syrups and infusions. Some of the molds produce citric and ox- 

 alic acids (Amer. Jour. Pharm., 1916, pp. 125 and 337). 



Aspergillus (Fig. 28) is distinguished from Penicillium (Fig. 



FIG. 28. Aspergillus, a yellow mildew. A, conidiophore with enlarged, more or less 

 spherical end, from which the fan-like series of chains of conidia' arise; B-E, successive 

 stages in the development of perithecium; F, section through a nearly ripe perithecium; 

 G, groups of young asci; H, a ripe ascus with 8 spores. A, after Kny; B-H, after De Bary. 



27) by the fact that the upper end of the hyphal branch or conidio- 

 phore is somewhat enlarged and more or less spherical. 



In addition to the conidiospores these Fungi sometimes produce 

 in the fall of the year, particularly when grown upon bread, asci 

 fruits (Fig. 27, C-F ; Fig. 28, B-E}. In this case two fertile ini- 

 tial hyphae wind themselves around each other, after which they 

 become surrounded with sterile branches which form a kind of 



