286 REPORT OF THE CONFERENCE ON GENETICS. 
The method used by Dr. Raunkiaer for determining the fructification 
of Taraxacum without fertilisation is a very simple one. We cut off with 
a razor the upper half of unopened flower-heads. By this drastic opera- 
tion the larger part of the corollas, of the styles, and the whole of the 
anthers and stigmas, are removed, while the basal parts of the corollas 
and the styles, together with the ovaries, remain. The “castrated ’’ head 
continues to grow, and at last we get ripe achenes, easily recognisable in 
the short pappus-rays. The fruits are quite normal, and produce normal 
offspring. 
Castration experiments with Hieraciwm species are similarly carried 
out, and the result has been the same—at least with regard to most of the 
species ; but there are some exceptions. I have mentioned the two sub- 
genera Ptlosella and Archieraciwm, both of which are very common in 
Europe and very polymorphic. The sub-genus Pilosella is characterised 
by leafless scapes and stolons, while the sub-genus Archieraciwm has a 
leafy stem and lacks stolons; the more technical systematic differences 
between the sub-genera are omitted here. 
1. In America, where the Hieracia are of much slighter importance 
than in Europe, we find a little sub-genus Stenotheca, which reminds 
us in the vegetative parts of Archieracivwm, but it is more slender and 
has smaller flower-heads, rather like those of a Cvrepis. I have two 
species of this sub-genus under cultivation, and these two species do not 
set fruits at all after castration, while the intact heads give fruits of which 
at least a good many have the power of germination ; consequently 
the species in question are quite typical with regard to the fertilisation 
phenomena. This result agrees well with the cytological examination 
made by Dr. Rosenberg. 
2. The results are very different in the sub-genus Archieraciwm. My 
experiments include fifteen species belonging to very distant sections of 
the sub-genus, and among them only one species, H. wnbellatwm in the 
widest sense (sensu Jlatiore), needs fertilisation, all the others giving 
plenty of fruits after castration. The only exception is the same species 
which Mendel used for his above-mentioned hybrids, and which lately 
have been examined from a cytological point of view by Prof. H. O. Juel. 
This author has found that the development of the egg-cell in H. wm- 
bellatwm was normal. On the other hand, Prof. $8. Murbeck has studied 
the cytology of the ovule of three other species of Archieracium, and he 
has stated that the egg-cell grows out to an embryo without fertilisation, 
i.e. apogamically. I think we may conclude that the same is the case in 
the fourteen species castrated by me. 
3. In the sub-genus Pilosella, again, the condition of affairs is more 
complicated. I haye used six species in my experiments, and five of 
them have given ripe fruits after castration, while one, H Awricula, 
needs fertilisation. Among the species with apogamy there are, for 
example, the well-known H. Pilosella and H. awrantiacwm, and also 
a rather curious species which for years has been cultivated in the 
Botanical Garden of Copenhagen. It belongs to the species with many-. 
flowered corymbs and is related to H. magyaricum, a species-group 
which is common in the eastern part of Central Eurcpe; Prof. Block, 
of Lemberg (Galicia), has described it under the name H. eacellens; it 
