LABOULBENIALES 395 



which can branch and proceed independently to form asci. By this 

 insertion of a new phase, the activity of the gametangia increases; from 

 a gametangium may arise several gonotoconts. Thus, phylogenetically 

 considered, the reduction caused by the privileging of a small number of 

 gametangial nuclei was overcome. 



Still the phylogenetic development of the Ascomycetes is most obscure. 

 We need only cite the contradictions between the Pencillium and the 

 Pyronema types, the Taphrina type and the Laboulbenia type. In any 

 case, within the Plectascales has somehow been developed the hook form 

 of the Pyronema type which, on account of its distribution in the Ascomy- 

 cetes and its character as bridge to the clamp mycelium of the Basidio- 

 mycetes, has become the most significant form of ascogenous hyphae. 

 While in Pyronema confluens, the hook tip can occasionally fuse with the 

 stipe cell, whereby the stipe nucleus migrates into the tip and develops 

 it to a branch, in some higher forms, as Helvetia elastica and Parmelia 

 acetabulum, this fusion of hook tip with stipe cell becomes the rule. Only 

 in them the nucleus of the tip migrates back into the stipe, so that branch- 

 ing is absent and clamp formation is entirely similar to that of the 

 Basidiomycetes. 



Simultaneously with the degeneration of sexuality, the ascogenous 

 hyphae lose their specific character. They still arise only as a result of 

 pseudogamous copulation between vegetative hyphae somewhere in the 

 tissues of the fructification, and penetrate it for a long distance. Since 

 these ascogenous hyphae more and more assume the character of vegeta- 

 tive hyphae, it is comprehensible in certain forms, as in Ascocorticium, 

 that asci appear to arise directly from vegetative mycelia. If we imagine 

 this development proceeds one step further, in that the ascogenous hyphae 

 (like vegetative hyphae) become adapted to independent food intake 

 (which is perhaps already the case in some Ascomycetes, as the Ascocor- 

 ticium group) we come to the clamp mycelium of Basidiomycetes. 



And finally, from Dipodascus there has been an ascent in formation of 

 fructifications so that in the highest forms, as in the higher Hypocreales 

 and Pezizales, are evident the same principles of increase of surface which 

 we shall again meet in the Basidiomycetes. Hand in hand with degenera- 

 tion of sexual organs goes the shifting of their formation in respect to that 

 of fructifications; while in the lower forms the ascogonium introduces the 

 development of the fructification, in the highest forms, the fructifications 

 arise by vegetative stimulation and the functionally and morphologically 

 degenerating ascogonia (generally in the majority) develop on them. 

 Here also is a short step to the Basidiomycetes. 



