GROUPS OF PLANTS. 27 



They are capable of germinating on almost everything, as old 

 shoes, old paper, as well as on bread and other articles of the 

 household, and are commonly found on " moldy drugs," in a num- 

 ber of pharmaceutical preparations, as syrups and infusions, and 

 even in solutions of inorganic as well as organic chemicals. 



Aspergillus (Fig. 18 j is distinguished from I'enicillium (Fig. 

 17) 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. 17, C-F ; Fig. 18, B-E). In this case two fertile ini- 

 tial hyphge wind themselves around each other, after which they 

 become surrounded with sterile branches which form a kind of 

 loose tissue, more or less cellular in structure, that finally develops 

 into a yellowish leathery wall. This body, which may be regarded 

 as a closed ascocarp, is known as a perithecium (Fig. 17, F ; Fig. 

 18, F). As a result of the conjugation of the fertile cells, asci 

 (Fig. 17,6", H, J ; Fig. 18, G, H) develop within the perithecium. 

 which are more or less spherical or ellipsoidal and contain from 

 four to eight spores (ascospores) (Fig. 17, K; Fig. 18, //). 

 After maturity the cellular tissue around the asci dries up and dis- 

 integrates, the walls of the asci dissolve, and the ascospores are 

 liberated from the perithecium by slight pressure. The spores 

 lie over winter and then germinate, producing a mycelium from 

 which conidia first develop and afterwards the perithecia, thus 

 repeating the life history of the plant. 



Ergot. Another Ascomycete of special interest is the 

 fungus known as ergot {Claviceps purpurea). The spores of this 

 fungus germinate on the flowers of certain grasses. The myce- 

 lium penetrates the walls of the ovary, absorbing the nutriment. 

 After a time the mycelium develops on the surface, and from 

 this short conidiophores arise bearing small ovoid conidia (con- 

 idiospores) (Fig. ig,A). The mycelium secretes a sweet fluid, the 

 so-called honey dew which attracts insects, and thus the conidia 

 are carried to other plants. As the conidia are capable of immedi- 

 ate germination the so-called " ergot disease " rapidly spreads 

 during the flowering season of the host plants. After the forma- 

 tion of conidia ceases, the mycelium forms a dense mass which is 



