A. H. Trow 



267 



There appears to be a distinct impediment to the production of green- 

 stemmed, non-radiate plants, and therefore a tendency to the formation 

 of a 9 : 3 : 4 ratio. 



The examination of the ^3 generation of the cross lanuginosua 

 X multicaulis for stem colour was attended with difficulties. It is 

 difficult to arrange the plants under the three types GG, Gg and gg, 

 owing possibly to the direct colour modifications due to the environ- 

 ment. Much more work is required before a clear and complete 

 explanation can be given of the results in the case of this cross. 

 Six colonies were examined, all growing together in the open air, 

 under conditions as similar as possible. The outside plants of each 

 colony might have been expected to shew differences when compared 

 with the inside ones, but none were noticed, although specially looked 

 for. On the other hand, a certain efifect of shading was very obvious ; 

 when the earlier plants were uprooted for examination from some of 

 the beds, the later ones received considerably more light and air, and 

 their stems quickly acquired a certain amount of red colouring matter. 

 This kind of response is well known to botanists, and appears to be 

 more or less independent of the colour factors for stems that we are 

 considering here. The result of the examination of these six colonies 

 for stem colour is presented in 



TABLE XVIII. 



Exp. 

 Exp. 64 



Culture 

 No. 



Cross 



33 



Exp. 66 35 

 Exp. 67 36 



Exp. 68 37 



Exp. 69 38 

 Exp. 70 39 



Lanuginosus x ) 

 multicaulis ; 



Lanuginosus X | 

 multicaulis ) 



Lanuginosus x ) 

 multicaulis j 



Lanuginosus x ) 

 multicaulis f 



Lanuginosus x ) 

 multicaulis \ 



Lanuginosus x ) 

 multicaulis j 



Gen. 



Estimated 



constitution 



of parent 



No. 



of 



plants 



Types 

 of Stem Colour 



HhRrGg 49 

 HhRRGg 96 



GG 

 13 



Gg 

 20 



77 



16 



19 



Bemarks 



HHYyRRGG 

 HHYYRrGg 



49 



97 



49 — 



F3 HHYyrrGg 92 

 F3 HHYYRRGg 48 



Difficult to distin- 

 guish GG from Gg 



All plants, reddish 

 green 



Colony difficult to 

 sort. GG not 

 sharply defined 



Possibly all plants 

 were gg 



Possibly all plants 

 were gg 



It does not seem desirable to spend much time in analysing further 

 these incomplete results. Additional experiments are necessary. Never- 

 theless all are of interest. Green is apparently recessive. It is certainly 

 easier to pick out the pure greens (gg), for the pure reds are apt to pass 

 over more or less gradually into the reddish greens. 



