CHAPTER L. 



FUNGI {continued). 



ASOOMYCETES. 



I. The Ascomycetes constitute a class of the Higher Fungi, 

 including more than 10,000 species. They all have septate 

 hyphse and their main distinguishing feature is the possession of 

 a sporangium of definite shape and containing a limited and 

 definite number of spores. The sporangium is termed an ascus, 

 and is generally club-shaped or oval in form. 



When the ascus is young it contains a single nucleus em- 

 bedded in finely granular protoplasm. This nucleus subse- 

 quently divides first into two, then into four, and finally into 

 eight nuclei : the latter afterwards surround themselves with 

 small portions of protoplasm and a cell-vrall, and become non- 

 motile spores, each of which is -termed an ascospore. 



An ascus generally contains eight ascospores, although in 

 some species two, four, or a larger number are present. • 



The ripe spores are often ejected from the ruptured apex of 

 the ascus with considerable force. 



In the simplest representatives of the class, the asci are 

 exposed and situated directly on the mycelium, but in the 

 higher forms, which are the most numerous, the asci are 

 enclosed in fruit bodies or ascocarps composed of closely 

 interwoven septate hyphse often resembling a parenchymatous 

 tissue of polygonal cells. 



Usually preceding the formation of ascospores, the fungi are 

 very extensively reproduced by means of conidia. Many species 

 are pleomorphic, producing several distinct types of conidia 



?45 



