206 NATURE OF THE SAC FUNGI 



simplest cases one or more sacs. These bodies are known as asci 

 (sing, ascus) and they contain more frequently eight spores, 

 called ascospores (Fig. 141), which must be distinguished from 

 the spores or conidia mentioned above. The gametospore germi- 



FIG. 138. The green mould, Penicillium, one of the most common of the 

 Sac Fungi. The hyphae of the branching mycelium is composed of cells 

 and the spores or conidia are formed in chains that are arranged in brush- 

 like clusters at the ends of the erect hyphae. 



nates as a parasite on the mother plant as in the red algae. 

 The sexual process results, in the majority of forms, not only 

 in the formation of asci, but numerous hyphae from the my- 

 celium are also stimulated to growth and become associated 

 with the asci in various ways. As a result bodies of various 

 forms, called ascocarps or perithecia, are developed which often 

 become the conspicuous part of the fungus (Figs. 143, 144). 

 The ascospores germinate immediately or after a period of rest 

 and form a new mycelium. It should be stated that the asco- 

 carps have not been connected, in many cases, with sexual proc- 

 esses, and it is inferred that sexuality has been lost along with 

 other characters as a consequence of the degeneracy resulting 

 from parasitic and saprophytic habits. Only a few of the more 

 important orders will be discussed. 



83. Order a. Yeast or Saccharomycetes. These fungi are 

 unicellular plants and many regard them as reduced ascomycetes. 

 They do not produce a mycelium, but consist of rather oval cells 

 which multiply by a budding process shown in Fig. 139, A, 'B. 



