72 



PLECTOMYCETES 



[CH. 



substance, readily soluble in alcohol, in the form of a thick, brittle pellicle. 

 These constitute the protective sheath (fig. 30 c), by the decay of which, 

 after the disappearance of the nutritive hyphae and later of the ascus walls, 

 the spores are finally set free. The ascospores are spherical or lenticular 

 often with a sculptured epispore. 



In most species of Penicillium reproduction takes place almost entirely 

 by means of the abundant conidia borne in chains on the branched, brush- 

 like conidiophores (fig. 3 1 ). Ascocarps are rare, and a detailed study of their 

 development has yet to be made. 







Fig. 32. Penicillium glaucum Link; 

 conjugating cells, x 630 ; after 

 Brefeld. 



Fig. 31. Penicillium glaucum Link; conidiophores 

 and conidia, x 500. 



Brefeld, in 1871, succeeded in obtaining perithecia of P. glaiicum> by 

 cultivating his material under reduced oxygen pressure. He cautiously 

 moistened slices of bread with distilled water, and after six or seven days, 

 when the development of the mycelium was proceeding energetically, 



1 Penicillium glaucum Link = /'. crustaceum L. 



