348 C- H. Ostenjeld. 
unreduced number of chromosomes. Therefore I speak of apogamy, 
not of parthenogenesis. 
II. 
The genus Hieracium has been divided into three sub-genera, 
which are widely separated from each other, and which also differ 
as regards their apogamy. 
One sub-genus, Stenotheca, is rather small; it has only one 
species in Europe, H. staticifolium of the Alps, and several species 
in America. I have had two American species and the European 
one in culture, and have found that none of these three species gives 
fruit after castration. One of the American species has been 
studied from a cytological point of view by Rosenberg and was 
found quite normal. Thus the sub-genus Stenotheca, as far as it has 
yet been investigated, is quite normal and requires fertilisation for 
producing seeds. As far as I know, no polymorphy is found in it; 
and on tbe whole, in contrast to Europe, polymorphy in Hieracium 
has not been recorded from America. 
The second sub-genus Archieracium, on the other hand, is very 
polymorphous ; the greater number of the many minor species thus 
far described belong to it. Its species are veiy numerous in Europe; 
some occur also in Asia, and a few in America. Very probably, in 
Europe, new forms of this sub-genus are appearing at the present 
time, and it is an interesting fact that many of the described species 
have an extremely limited distribution, which points to a very 
recent origin. 
I have made experiments with many (about 65) species or 
forms of this sub-genus and have found that nearly all are apo- 
gamous, and by counting the numbers of fertile seeds in castrated 
and in non-castrated heads, 1 think I have shown that nearly all 
species examined are absolutely apogamous, i.e., no flower is capable 
of fertilisation. Only two species, namely H. umbellatum (which is 
rather a group of species) and H. virga-aurea, require fertilisation 
for developing fertile seeds, giving no seeds after castration. 
Nevertheless I have had one form of H. umbellatum which is apo¬ 
gamous, and in this case the number of fertile seeds in the castrated 
heads was not so large as the number in non-castrated heads. 
This means, probably, that some, but not all, of the flowers of a 
head are apogamous, some requiring fertilisation. A few other 
species are likewise only partly apogamous, judging from the 
comparative number of fertile seeds in castrated and non-castrated 
heads. Thus we have three stages in the development of apogamy : 
