396 



BOTANY 



PART II 



Tlie development of the aiiotlieciuni may be described for Pyronema confluens, 

 in wliicli it was first thoroughly investigated by R. Harpf.ii. The fruit-body of 

 this siJecies is about 1 mm. across, and of a yellow or reddish colour ; it often 

 occurs on spots where fires have been kindled in woods. The carpogonia are 

 especially large in this species, and several usually take part in tlie formation of 

 each apothecium (Fig. 326, A). The carpogonium or ascogonium consists of the 

 spherical, multinucleate oogonium, on the apex of which a multinucleate curved 

 cell, the trichogyne, is situated. The cylindrical, multinucleate antheridium 

 arises from a neighbouring hypha ; its ajiex comes into open communication with 



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Fk;. 3i6. — I'yioneirtKiconfluens. A, Kuiiiiiieiit of aiitapdUieciuin. consisting of three oogonia (o*;), 

 with trichogynes (t) and tln-ee anttieridia (a). B, Fusion of the antheridium and the tip of tlie 

 trichogyne. C, The basal wall of the trichogyne having been absorbed, the male and female 

 nuclei are grouped in the centre of the oogonium. D, Separation of the oogonium from tlie 

 trichogyne by means of a new partition wall. Formation of the ascogenous filaments («,•-/). K, 

 Longitudinal section through a young apothecium. ««', Asci. (AfttT R. Harper. A, E 

 X about 150, B-D x about 300.) 



the tip of tlie trichogyne by the breaking down of the intervening walls. The 

 male nuclei first wander into the trichogyne cell, and then, by the breaking down 

 of the basal wall of the latter, into the oogonium. The egg-cell then becomes 

 limited from the trichogyne by a new cell wall and sends out ascogenous filaments 

 containing the conjugated nuclei. These filaments branch and ultimately 

 terminate in a.sci {E), while the sterile hyphae and the paraphyses of the fructifica- 

 tion are derived from hyphae arising beneath the carpogonium. According to 

 Harper the male and female nuclei fuse in pairs with one another in the 

 carpogonium. More recent investigations by Claussen show that they only place 

 themselves side by side, and in the ascogenous hyphae divide conjugately, Imt 

 remain distinct from one anotlier. The fusion of a descendant of a male nucleus 

 with the descendant of a female nucleus does not take jilace till tlie develo2)ment 

 of the ascus. 



