[Vol. 2 



348 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



them the real act of fertilization (Strasburger, '00, '04, '05). 

 Remarks on the origin of the specialized ascus. — In the 



direction of progression from the generalized ascus by split- 

 ting up of the zygote, the diploid phase has been prolonged 

 and the number of spores multiplied. The filamentous out- 

 growths of the zygote, or its equivalent, provide numerous 

 terminal cells of restricted size suitable for the production of 

 a small number of spores in each, following the meiotic divi- 

 sions of the fusion nucleus which terminate the diploid phase. 



The situation in species with polysporic asci, where the 

 spores result from numerous divisions of the fusion nucleus, 

 is interpreted by some as a germination phenomenon (Over- 

 ton, '06), but it seems to me more comprehensible to regard it 

 as a retention of a primitive feature existing in certain phyco- 

 mycetous ancestors, and characteristic also of primitive As- 

 comycetes like Dipodascus. 



The formation of internal non-motile spores through free 

 cell formation in the zygote, under conditions adapted for dis- 

 persion by ejection from either the generalized or specialized 

 ascus, may be sufficient to account for the distinctive processes 

 of spore formation in the sac fungi. In the oogonium of 

 Saprolegnia, functional nuclei in the oogonium are very simi- 

 lar to the nuclei of the ascus preceding ascospore formation. 

 The nucleus is provided with a prominent central body at its 

 pointed end from which kinoplasmic radiations extend (Har- 

 tog, '95; Claussen, '08; Miicke, '08). 



In most of the Ascomycetes the cytoplasm in the ascus is 

 differentiated into epiplasm and spore plasm, the former as- 

 sisting in the ejection of the ascospores. This separation of 

 the plasm may have been one of the direct causes of the 

 peculiar method of ascospore formation. 



NOTE IV 



THE PHYLOGENETIC RELATION OF THE TBIOHOGYNE AND SEXUAL APPARATUS OF 



THE ASCOMYCETES AND THOSE OF THE RED ALGAE 



The sexual apparatus of the Ascomycetes, particularly the 

 trichogyne and the so-called spermatia, is generally conceded 



to be the strongest evidence in support of their phylogenetic 



