256 Non-Isolahlc Races. 



I found it to be dependent only to a very slight degree on 

 the former but in a high degree on the latter. 



The first question that presented itself was: To what 

 principles of distribution does the number of petals on 

 the individual plants correspond. Is this number de- 

 termined by the situation of the flower or by external 

 factors or by both? With regard to the position of the 

 flower Braun in his Verjunguiig distinguishes between 

 a strengthening and a weakening system of branching. 

 In the former the branches increase in strength, though 

 often but slightly, with each new degree of division; in 

 the latter each secondary branch is weaker than the 

 branch on which it is borne. Ranuncithis bulbosus be- 

 longs to the former category (see Fig. 49 on page 244). 

 The main stem (E) is surpassed by the vigorous lateral 

 shoots (S), which arise directly from the tuber, and 

 these in their turn are excelled by their own (tertiary) 

 branches (T in the figure). The same thing continues 

 with further growth until ultimately the process is re- 

 versed and weaker branchlets are produced. The more 

 vigorous a branch is, the larger and stronger, as a rule, 

 will be its flower. 



If we now compare the number of petals on the 

 flowers of this half race, with their position on the 

 branches of the various orders, we are often struck by 

 an apparently definite correlation. But this is only due to 

 the fact that such cases produce a more vivid impression 

 than the opposite ones. When a detailed record is made 

 the latter are found to be just as numerous as the former. 

 In September 1892 I determined the number of petals, 

 and the position on the plant, of 1197 flowers on 82 

 plants ; and plotted a curve for each position. Here how- 

 ever I only give the means of the curves. 



