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A TEXTBOOK OF THEORETICAL BOTANY 



The Development of the Sex Organs 



The cells of the mycelium are multinucleate and form a system of threads 

 which ramify through the substratum. Among these hyphae branching is 

 rare, but at certain points one or more forks appear from which branches 

 grow upwards and form a small tuft. These filaments then branch dichoto- 

 mously, and the terminal cells of paired branches become differentiated into 

 a functional antheridium and a female organ, the oogonium or ascogonium 

 (Fig. 254). Behind these are cut off one or two stalk cells, so that the 



Trichogyne 



Ascogonium 



Antheridium 



Fig. 254. — Pyronema confluens. Group of ascogonia 

 with attached antheridia. 



antheridium forms a two- or three-celled branch, made up of uninucleate 

 stalk cells and a multinucleate antheridium. The female branch consists 

 similarly of one or two stalk cells, the swollen ascogonium and a trichogyne 

 formed as a tubular process from the distal end of the ascogonium. Both the 

 ascogonium and the trichogyne are multinucleate but unicellular. 



As growth continues the nuclei of both the ascogonium and the antheridium 

 increase in size, while those of the trichogyne remain small and finally 

 disorganize. 



Fertilization 



The trichogyne now comes into contact with the antheridium, and the 

 wall between becomes dissolved. The male nuclei which have united into a 

 cluster in the centre of the antheridium now migrate into the trichogyne, 

 whose own nuclei have meanwhile disappeared. At the same time the wall 

 separating the trichogyne from the ascogonium disorganizes and the nuclei 

 of the ascogonium become grouped at its centre, while the surrounding 



