256 Non-Isolable 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 Verjilngung 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. Ranunculus 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. 
