8. Ikkno 4o 



reality just as bhick ixs thow o( this ih'nv fnnn, tluir coltnir is |Nirtly 

 coiicchIihI by haii-s covi'riiij; tlu'iii. In (lii« lu'w fonii there are twn 

 kindji of fciimle plant-H, the one |H>.sHeHHi!ig red Hti^nnax and the other 

 green onen. In 191 (>, when they appeared for th** firnt time, a few 

 femiile catkins (riowers with green stignuus), which <lid not look «juit«' 

 healthy, wen* fertilis*Hl with jHiIlm from the mah* catkins of iju- sjuim' 

 type, and a few see<is wiTe obtained, w hich »iid not );«'rminat;4*. This 

 year(l!)lS) I re|H'ati'd the same fertilisation (flowi-rs with rc(| stigm;i,s), 

 and got many si'cds, which were able to germinate and have given lise 

 U» a certain number of seedlings. Whether or not the latter breed 

 true t-o the ty|>es of their parents is of cours<' yet unknown ; it is, nev<r- 

 thele^, not unlikely that this new type is a muUint — possibly a 

 loss-mutant priKJuced on account of the loss of the factor for the* 

 hair-formation — and arising after hybridisiition. Mutation after hyl^ri- 

 disation hsis, jus is well known, been sometimes discovered in (Jenot/ieni 

 by de Vries', (Jates-, etc., and also in HKbu^s by Lidfoi-ss'. 



What I have described above about the formation of the two tyjKJS 

 of plants afti'r hybridisiition between S. gvacilistyla and S. inultinervis 

 is merely the description of the results actually gained, and I must now 

 go into their interpretation. The question is, should the appearance of 

 both (i-type and J/-typc otispring in F^ be regarded ;is the result of 

 segregation, or may this fact be explained in any other way ? The 

 exact answer to such a question cannot be given without further 

 breeding experiments, and I am, for the present, only able to make 

 certain hypotheses about it. 



According to the first hypothesis one of the two original parents, 

 either S. gracilistyla or aS*. nudtinervis, should be regarded as being 

 heterozygous, at least in respect to the catkin character under con- 

 sideration. Thus if, for instance, we denote the (r-type character by 

 G and its absence, i.e. the Jl/-type one, by g, and if we further give to 

 S. gracilistyla and S. multiuervis the formulae Gg and gg, respectively, 

 we have in the fertilisation of the two ASWi^-species a back-cross 

 Gg X gg = Gg -f gg, thus explaining the production of the two types of 

 plants in F^. It will be of course the same, if we consider S. multinervis 

 to be heterozygous and S. gracilistyla to be homozygcjus reganling this 

 character. Is then either of the two *S'(//ia;-species under consideration 



* See, for instance. Die Mutationstheorie, Bd i. pp. 211, 212 and Bil ii. pp. 425, 426; 

 also GrupptniceiKe Artbihhtng, p. 302 flf. 



* The Mutation Factor in Evolution, p. 2HG ff . 



' Zeits.f. ind. Abstaminunys. und Vererbumjulchn', Bd xii. l'U4, pp. 1 — 13, 



