Further Studies on the Apogamy and Hybridization of the Hieracia. 275 



apogamj' does not originate as a reaction against sterility of the pollen 

 (the case of H. aitraniiacuui). 



Taking all the quoted opinions together I regard the above given 

 sentences of H. Winkler as a good expression for the present position 

 of the question with regard to the origin of apogamy. 



I may sum up my views on these matters in the following way, 

 bringing together what the investigations, in my opinion, have proved : — 

 There is, at least with regard to the dicotyledons, an evident relation 

 of apogamy to polymorphism, but it is not allowable to 

 draw any conclusion as to causality between them or as to 

 the age of the apogamy. 



The supposition of Strasburger and Tischler, that apogamy is a 

 secondary thing while degeneration of pollen is primär}^ is not tenable. 



Winkler's supposition, too, that apogamic plants do not vary or 

 mutate, is scarcely correct. 



As to Hieracium it must even be considered unlikely that 

 the species now existing have originated before apogamy 

 arose. Nothing hinders the supposition that new species can originate 

 from apogamic parents, and we may compare this case with the 

 inheritable bud-mutations which have been studied, e. g. by Wett- 

 STEIN (1904) and W. JOHANNSEN (1908). The results of my hybridi- 

 zation experiments, mentioned in the earlier part of this paper, point 

 in that direction. It has there been proved that a mutant has arisen 

 in F, of an apogamic hybrid; — certainly only one specimen. 



The hybridization experiments show further that hybrids are 

 able to propagate apogamicaUy and then are constant. This makes 

 it allowable to conclude, i" that \Niihin Hieracium the evolution 

 of new species goes on coincidently with the existence of 

 apogamy; 2" that the new species reach constancy at once 

 just because of the apogamyi); 30 that the polymorphism is 

 correlated to the apogamy in such a manner only that apo- 

 gamy, through the constancy of the species, apparently 

 furthers the polymorphism. 



1) Almost the same conclusion has been drawn by R. v. Wettstein (1904, p. 517), 

 who says, "Es ist leicht verständlich, daß bei solchen Pflanzen [Alchimilla and Hie- 

 racium], bei welchen die Rückführung in den ursprünglichen Typus durch Kreuz- 

 befruchtung ausgeschlossen ist, jede auftretende Mutation sofort fixiert 

 werden und — insofern die so entstehende Pflanze nicht unzweckmässig ist — zur 

 Neubildung einer Art führen kann. Der Polymorphismus solcher Gattungen ist dann 

 — zum Teile wenigstens — direct der Ausdruck der Mutationsfähigkeit derselben." 



18* 



