Særtryk af Botanisk Tidsskrift. 27, Bind, 3. Hæfte. København 1906, 
iv 
Arbejder fra den Botaniske Have i Kobenhavn. Nr. 3: 
Experimental and Cytological Studies 
in the Hieracia 
by C. H. Ostenfeld and O. Rosenberg. 
I. Castration and Hybridisation Experiments 
with some Species of Hieracia 
by LIBRARY 
NEW yo) 
C. H. Ostenfeld. YORK 
BOT AD i Al 
(With one plate.) a 
she 
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. 
Raunkier, that the statement in his paper on Taraxacum as 
far as Hieracium concerned perhaps needed some further investi- 
gations'), and he answered that he agreed, as most of his experi- 
ments with Hieracia 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 Cichorieæ. The results of our experiments were 
1) 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. 
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