Experimental and Cytological Studies 

 in the Hieracia 



by C. H. Ostenfeld and O. Rosenberg. 



I. Castration and Hybridisation Experiments 

 with some Species of Hieraeia 



by 



C. H. Ostenfeld. 



(With one plate.) 



I. Introduction. 



In the early days of June 1903 I observed in the Botanical 

 Garden of Copenhagen a flowering specimen of Hieracium hyparc- 

 ticum, raised from seeds from East Greenland which were brought 

 home by Mr. C. Kruuse. Remembering the polymorphism of the 

 genus, it occurred to me to make castration experiments with it in 

 the same manner as C. Raunkiær (1903) had done with our 

 Taraxaca. I therefore cut off with a razor the upper half of some 

 unopened flower-heads, removing in this way the anthers and the 

 stigmas. Some days after I saw, that the heads had continued to 

 grow and that the achenes had begun to develop. I then told Mr. 

 R a un k i ær, that the statement in his paper on Taraxacum as 

 far as Hieracium concerned perhaps needed some further investi- 

 gations 1 ), and he answered that he agreed, as most of his experi- 

 ments with Hieraeia had been broken off. Both he and I began 

 now to work in the same manner, taking several species of the 

 genus into consideration, and also extending our experiments to 

 other genera of the Gichorieæ. The results of our experiments were 



l ) Mr. Raunkiær says (1903, p. 135): I castrated some heads of species of 

 Hieracium, Crepis etc.; the heads continued to grow, but only to a certain 

 point, and no fruits which were able to germ, were developed; my experi- 

 ments made in the summer of 1902 were only few and comprehended only 

 few species, why I intend to continue with them. 



Botanisk Tidsskrift. 27. Bind. 15 



