ER 
II. Castration Experiments. 
In the summer of 1905 Mr. Raunkiær and I castrated about 
20 species of Hieracium. The experiments were carried out in 
June—July, but as we began so late, we could get only few species 
of the subgenus Pilosella, because they flower a little earlier than 
the species of the other common subgenus, Archieracium. 
In the following summers (1904 and 1905) I have continued 
and extended the experiments. Some few species more of Archie- 
racium have been examined, further several forms of subgen. Pilosella 
and finally two species of the subgenus Stenotheca, of which all the 
species (one excepted) are American. I should like very much to 
get seeds of other species, especially if they belong to more re- 
markable sections. It is very difficult to obtain species other than 
the usual ones of Archieracium and Pilosella, which every year 
appear in the seed-catalogues of the botanical gardens"). I should 
be glad, if botanists in America would supply me with seeds of 
Hieracium, : 
The experiments were done in the same way as Raunkiær 
has described in the case of Taraxacum: We chose flower-heads 
which are very near to open, and cut off with a razor the upper 
half of the heads. The part cut off consists of the upper half of 
the bracts, the coloured part of the corolla, the upper part of the 
staminal filaments, the anthers and the stigmas together with the 
upper part of the styles. The surface of the remaining part of 
the heads is soon covered, more os less, with coagulated latex and 
shrivel. It is then unreasonable to suppose that an accidentally 
present pollen-grain should be able to germinate and penetrate 
through the wounded style to the ovary. Further, supposing that 
it may have happened sometimes, this explanation fails when we 
get nearly all the fruits in a head developed. The two only possi- 
embryosacs formed in this way give rise to embryosacs which conse- 
quently are quite normal and may be capable of fertilisation (compare H. 
excellens >< aurantiacum). But commonly the mothercell of embryosac is 
displaced and obliterated, while an aposporical embryosac supersedes. 
The third, but rarer case is, that apogamical embryosacs (as in Taraxa- 
cum) are developed. In the two last cases the eggcells have the un- 
reduced number of chromosomes and are capable to form seeds without 
fertilisation”. 
Still I have got more than 70 samples of seeds, which now are growing 
in our Botanical Garden ; but they belong nearly all to the Archieracia and 
the Piloselloidea. 
1 
— 
15* 
