120 Origin of New Forms in Hieracium 



This new form — H. rigidum Gamma — differs from the original Alpha 

 in the following characters (compare the plates) : 



1. It is somewhat lower and with more divaricating branches. 



2. The leaves are distinctly broader than in Alpha. 



On the other hand there is no marked difference with regard to the 

 involucral bracts nor to the shape and size of the flowerheads, only a 

 slight tendency towards the Beta-iovm. The same is the case with the 

 colour of the involucral bracts. 



As to the vigour and height the new (9am7na-form is intermediate 

 between Alpha and Beta, but it has broader leaves than either of them. 



There is a peculiarity which may be of some importance. The original 

 form {Alpha) is very fertile after agamization; nearly all achenes are 

 developed and contain sound-looking germs. In Beta I have always 

 found many empty achenes and the germinating power is less, while in 

 Gamma the fertility is nearer to Alpha, although not reaching it. 



My experiments show that it is possible to produce nevj forms apo- 

 gamically from, constant apogamic forms of Archieracium, these new 

 forms being themselves apogamic and at once constant. They may be 

 called " apogamic mutants." Most probably the numerous microspecies of 

 Archieracium found in nature have arisen in that maimer. 



There seems, to judge from the experiments, to be a contrast between 

 the origin of species in the two subgenera ; in Pilosella the forms arise 

 by means of hybridization, in Archieracium by means of " apogamic 

 mutation." But is this contrast radical? 



In Pilosella we find species which are partly apogamic and partly 

 sexual as they are able to produce hybrids after fertilization with other 

 species, and at least some of these species are themselves probably — to 

 judge from the polymorphy of the jPj-generation — to be considered as 

 hybrids. The hybrids produced are apogamic like their parents and 

 owing to apogamy at once constant. If we now cultivate in large 

 numbers such a new form produced by means of hybridization, would it 

 then be possible to get single deviating individuals, as I have shown 

 with regard to Archieracium ? I have not yet made any thorough ex- 

 periment, but I should think that we may answer the question in the 

 affirmative. A single experiment which was not completed points in 

 that direction : in a large culture of a race of H. aurantiacum — all from 

 seeds obtained after agamization of the heads of a single plant— a single 

 much deviating individual was found, but unfortunately it died before 

 flowering. Supposing that this fact is not due to any experimental 

 error, it speaks in favour of my hypothesis that also within the newly 



