DISCOMYCETES 



[CH. 



130 



ascogenous hyphae, replacing, as in Humaria rutilans, the obsolete sexual 



fusions, and preceding the fusions in the asci. Carruthers has studied the 



Fig. 90. a. Hdvella crispa (Scop.) Fr. ; b. and c. Morchella vulgaris Pers.; after Boudier. 



nuclear divisions, and finds two chromosomes in the vegetative and four in 

 the fertile hyphae. Four again appear in the first and second (meiotic) 

 divisions in the ascus, after the second fusion has taken place, and two are 

 recorded in the telophase of the third division, and in the mitosis in the 

 spore. The ripe spore normally contains eight nuclei. 



In both species, after an ascus has arisen from the penultimate cell of 

 a hypha, the terminal cell may grow on, giving rise to others, and may fuse 

 before doing so with the third cell of the hypha, which is the stalk-cell of 

 the previously formed ascus. 



In Morchella esculenta the nuclear divisions of the ascus have been 

 studied by Maire. After observing eight chromatin bodies in the prophase 

 of the first division in the ascus, he found four in the prophase and anaphase 

 of the third, and in the divisions of the spore nuclei ; this corresponds closely 

 with Carruthers' results in Helvetia crispa. 



HELVELLACEAE : BIBLIOGRAPHY 

 1905 MAIRE, R. Recherches cytologiques sur quelques Ascomycetes. Ann. Myc.iii,p. 123. 



1910 McCUBBlN, W. A. Development of the Helvellinaceae. I. Helvetia elastica. Bot. 

 Gaz. xlix, p. 195. 



191 1 CARRUTHERS, D. Contributions to the Cytology of Helvella crispa. Ann. Bot. xxv, 

 p. 243. 



