No. 557] PAETHENO GENESIS IN NICOTIAN A 



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einer Species (oder Varietat) die sexuelle Zeugung ver- 

 loren geht und durch einen anderen Keproduktionsproc- 

 ess ersetzt wird." The word apogamy used with the 

 meaning intended by de Bary covers the term apomixis 

 of Winkler ; but as all the recent authors use the expres- 

 sion apogamy in a new sense, the introduction of a new 

 term seems justifiable. 



Apomixis is subdivided into vegetative propagation, 

 apogamy, and parthenogenesis: 



(A) Vegetative propagation consists of the replace- 

 ment of fertilization by vegetative formations (Aus- 

 lauferbildungen), arising of leafy (blattbiirtiger) shoots, 

 vivipary and similar examples of simple vegetative divi- 

 sion and the adventitious embryo formation from nu- 

 cellus cells. 



(B) Apogamy, the origin through apomixis of a 

 sporophyte out of vegetative cells of the gametophyte, is 

 subdivided into (a) somatic apogamy, if the cell or the 

 cell complex which produces the sporophyte possesses 

 the diploid chromosome number, and (b) generative 

 apogamy, if the mother cells of the sporophyte carry 

 only the haploid chromosome number. 



(C) Parthenogenesis, the apomictic origin of a sporo- 

 phyte from an egg, is subdivided into (a) somatic par- 

 thenogenesis, if the egg possesses a nucleus with the 

 diploid or unreduced chromosome number, and (b) gener- 

 ative parthenogenesis, if the nucleus of the egg is pro- 

 vided with only the haploid number of chromosomes. 



Winkler remarks, it is probable that the relations be- 

 tween somatic apogamy and apospory are very close, as 

 the former without the latter is surely not thinkable, 

 while the latter (the primary proceeding) may exist 

 without somatic apogamy. Examples of somatic apog- 

 amy are given, but no certain cases of generative apog- 

 amy are known; nevertheless, Winkler is very certain 

 that their existence is possible. 



Somatic parthenogenesis can be obtained in two ways : 

 first, it can combine with apospory, that is, a normal 



