390 



BOTANY 



PART II 



pairs of nuclei divide 



coujugately, and only in the young ascus do two nuclei, the 

 descendants respectively of a male and a female 

 sexual nucleus, fuse together. Thus the conjuga- 

 tion of the sexual nuclei is here delayed from the 

 carpogouium to the development of the ascus. 



So far as the results yet obtained allow of a 

 conclusion being drawn, the reduction division in 

 the Ascomycetes happens just after the fusion of 

 the two nuclei in the ascus. 



In the life-history of the Ascomycetes an 

 asexual reproduction by means of canidia often 

 precedes the development of the fructification. 

 The conidia are spores provided with a cell wall 

 which are budded off from the tips of simple or 

 branched hyphae, the conidiophores (Fig. 320). 



According to the construction of the 

 fructification we may distinguish in the 

 first place the orders of the Erysipheae, 

 Plectascineae, and Pyrenomycetineae, with 

 closed or vase-shaped fruit-bodies (peri- 



F.G. 3iv.-Portion ot ti.e hymeniu.a thecium), the Discomycetes with an open 

 of Morcheiia escuhnta. a, Asci ; fructificatiou (apothecium), and the Tul^er- 

 V, paraphyses ; sh, subhymeniai ^^^eae with a fructification that is at first 



open but becomes completely closed. 

 To these orders must be added the Exoasci, in which the asci 



an 



XX 



Kio. 'i\i. — Sphairothei:<i laiUKjnei. Fertili.sation and development of the perilliccium. 1, 

 Oogonium (og) with the antheiidial brancli (az) ajjplied to its surface ; 2, separation of 

 antheridium {an); 3, passage of the aiitheridial nucleus towards tliat of the oogonium; 

 /,, union of the nuclei ; 5, fertilised oogonium surrounded by two layers of hyphae derived from 

 the stalk-cell (st); 6, the multicelhilar ascogonium derived by division from the oogonium ; 

 the penultimate cell with the two nuclei {as) gives rise to the ascus. (After Haki'er.) 



arise from cells of the mycelium without the formation of any 



ii 



