Origin of Species in the Genus Hieracium. 353 
marks of this individual were so expressed that its appearance was 
quite unlike that of either parent. 
If we take all these facts and arguments together, it is, I think, 
permissible to say that new forms may arise by means of single 
variations, i.e., mutations, which may he classed under bud-mutations, 
as no fertilisation is required for their appearance. 
My position may be summarized in a few words, as follows: in 
Hieracium new forms arise by means of hybridisation and also by 
means of single variations; in both cases the prevailing apogamy 
supports their existence and constancy; thus polymorphism in the 
genus is correlated with apogamy, but it is not allowable to draw 
any conclusion as to causality between them. 
PRINCIPAL LITERATURE ON APOGAMY AND HYBRIDISM 
IN HIERACIUM. 
Correns, C. (1905). “Gregor MendePs Briefe an Carl Niigeli, 1866-1873. Ein 
Nachtrag zu den veroffentlichten Bastardierungsversuchen 
Mendels.” Abh. d. math. phys. Kl. d. k. sachs. Ges. d. Wissensch., 
XXIX, No. 3. 
Juel, H. O. (1905). “ Die Tetradenteilungen bei Taraxacum und anderen 
Cichorieen.” K. Svenska. Vet. Akad. Handl., 39, No. 4. 
Mendel, G. (1870). “ Uber einige aus kunstlicher Befruchtung gewonnene 
Hieracium- Bastarde.” Verb. d. naturf. Vereins Briinn, VIII, 
Abhandlungen. 
Murbeck, S. (1904). “ Parthenogenese bei den Gattungen Taraxacum und 
Hieracium." Botaniska Notiser, Lund, December 1904. 
Nageli, C. von, und Peter, A. (1885). “ Die Hieracien Mitteleuropas. 
I.— Piloselloiden.” Miinchen. 
Ostenfejd, C. H. og Raunkiaer, C. (1903). “ Kastreringsforsog med Hieracium 
og andre Cichorieae ” (English Abstract). Botanisk Tidsskrift, 
Kobenhavn, 25, Hefte 3. 
Ostenfeld, C. H. (1904). “ Zur Kenntnis der Apogamie in der Gattung 
Hieracium." Ber. d. Deutsch. bot. Ges., Bd. 22, Heft 7; and 
“ Weitere Beitriige zur Kenntnis der FYuchtentwicklung bei der 
Gattung Hieracium." Ibid., Heft 9. 
Ostenfeld, C. H. (1906). “ Castration and Hybridisation Experiments with 
some Species of Hieracia." Botanisk Tidsskrift, Kobenhavn, 27, 
Hefte 3. 
Ostenfeld, C. H. (1910). “ Further Studies on the Apogamy and Hybridisation 
of the Hieracia." Zeitsch. f. indukt. Abstamm. u. Vererbungslehre, 
III, Heft 4. 
Peter, A. (1884-85). “ Uber spontane und kiinstliche Gartenbastarde der 
Gattung Hieracium , sect. Piloselloidea:” Englers Botan. Jahrb,, 
Vols. 5—6. 
