THE FUNGI : ASCOMYCETES AND BASIDIOMYCETES 269 



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' Fig. 260. — Helvella elastica. Section through 



hymenium showing asci containing ascospores. 



as they do so. In this way a hymenial layer becomes differentiated on the 

 surface of the cap (Fig. 260). 



The Ascogenous Hyphae 



So far as is known no sex organs are produced. At a fairly early stage, 

 however, some of the hyphal threads form a mat of tissue a short way below 

 the paraphyses. These cells are multinucleate and considerably thicker 

 than the ordinary hyphae. It is from these cells that asci are produced by 



ASCUS CELL 



YOUNG ASCUS 

 A 



ASCUS 



ASCOGENOUS 

 HYPHAE 



Fig. 261. — Helvella elastica. A and B, Development of ascogenous hyphae. 

 C, Part of hymenium with paraphyses and developing asci. (After McCubbm.) 



