270 Inheritance in the Groundsel 



varieties of a variety; thus, Senecio vulgaris, Linn., var. multicaulis, 

 var. radiatus, vax. fimhriatus. 



Hairy varieties, in contrast to radiate varieties, are not produced 

 so readily. The non-radiate type of lanuginosus has not yet been 

 certainly obtained, nor a typically hairy praecox, erectus or multicaulis. 

 All, or nearly all, non-radiate types are less hairy than lanuginosus. 

 Consequently it is still somewhat doubtful whether the hair of lanu- 

 ginosus can be transmitted to the glabrous types quite unchanged. 



Analyses of the various segregations reveal the presence of eight 

 or nine factors, which may be represented in the usual way, accepting 

 provisionally, on account of its convenience, the theory of dominance 

 and the presence and absence hypothesis ; thus 



(a) Flower-factors. 



1. R, r. Factor for the radiate character. JJ = radiate. r= non-radiate. 



2. C, c. Factor for flower colour. C = yellow. c = cream. 



3. X, X. Factor for determining the development X inhibits the development of 



of the cream colour. cream colour. xc = cream, 



Xc = yellow. 



4. F, f. Factor for the development of the fim- F= normal rays. /= fimbriate 



briate character. rays. 



(b) Hair-factors. 



5. H, h. Main factor for hairiness. Jf= hairy. ^ = glabrous. 



6. Y, y. Factor modifying hairiness. Y depresses hairiness, y allows 



full development of hairiness. 



7. Z, z (?) Factor affecting the stimulation of If by Z reduces hairiness in R plants. 



R. z allows normal hairiness in 



R plants. 



(c) Stem Colour factor. 



8. G, g. Factor for red and green colour in stems. G=:red. gr = green. 



{d) Leaf Colour factor. 



9. L, I. Factor for leaf colour. i=dark green. Z= yellow green. 



These factors behave normally in segregation, except that in certain 

 cases gametic coupling has been recognised, viz. a gametic coupling of 

 the form IHU : \JIr : IhR : 2hr and possibly one of the form 



IHG : nHg : nhG : Ihg 



where w is a fairly large number. The latter type of coupling suggests 

 that certain combinations of characters may either be unrealizable or 

 realizable only with difficulty. 



