274 US ten leid. 



eine normale Befruchtung nicht mehr möghch war," and further (p. 146) : 

 „Apogamie hat sich als "Aushilfe" auf die Mutation und Sterilität des 

 Pollens eingestellt und ist nicht das Primäre und die Pollenobliteration 

 das Sekundäre." He thus expresses himself much more explicitly 

 than Str.\sburger. I think that these considerations are untenable, 

 as e. g. Hieracium anrantiaaim is a typical apogamic species, which 

 must be admitted already from Mendel's experiments (Correns 

 1905, p. 240), at least compared with mine, but it has good pollen 

 able to fertilize other species, as shown by the hybridization experiments. 

 This has been pointed out by Correns (1905, p. 249), and both 

 O. Rosenberg (1909, p. 160) and H. Winkler (1908, p. 136) have 

 used this fact as an objection against Strasburger and Tischler. 



H. Winkler again, as a further objection, points to TJialictrtim 

 pnrpnrascens and Taraxacum — both apogamic and with apparently 

 good pollen — , in which, without proof certainly, he supposes that 

 the pollen must be able "eine wirksame Befruchtung auszuführen". 

 Winkler himself is very cautious and weighs all possibilities for an 

 explanation of the origin of apogamy, as appears clearly from his 

 summarizing words, viz.: "Nach dem gegenwärtigen Stande unserer 

 Kenntnisse können wir also über die Faktoren, die phylogenetisch die 

 Einführung der habituellen Parthenogenesis oder Apogamie bewirkt 

 haben, ebensowenig etwas Sicheres aussagen als über die Natur der 

 Reizvorgänge, die jeweils im Verlauf der Ontogenese sie auslösen" 

 (p. 138). In his last chapter he advances the possibihty, that in 

 strongly mutating forms there is greater probability for the arising 

 of a mutant, which is apogamic or has apogamic tendencies, sooner 

 than in not-mutating forms, and as in such cases the "ausgleichende 

 Moment" of the fertilization is absent, the mutant can keep constant. 

 Here he refers to MURBiiCK's explanation of the remarkable constancy 

 of the Eualchiiiiillae. Still, this view implies, in his opinion, the following 

 supposition, "daß parthenogenetisch oder apogam gewordene Pflanzen 

 nicht mehr mutieren oder variieren können" (1. c, p. 148). I do not 

 see that this supposition is necessary or even correct, and here my 

 opinion agrees with that of StRASBURGER quoted above. 



Quite recently O. Rosenberg (1909) has put together the hitherto 

 known "Tatsachen" about apogamy. He points out the correlation 

 between apogamy and a great number of chromosomes, in contrast 

 to, most frequently, half the number in the non-apogamic species 

 within the same genus. He discusses the possible causes of apogamy 

 and, as mentioned above, refers among other things to the fact that 



