562 Curves of Compositae and Umhelliferae. 



became symmetrical in the two following years as can be 

 clearly seen by comparing curve A (1892) and B (1893) 

 in Fig. 117. 



§ 7. EQUILIBRIUM BETWEEN THE EFFECTS OF SELEC- 

 TION AND NUTRITION. 



These experiments were conducted with Chrysan- 

 themum segetum (Fig. 118), Coreopsis tinctoria and 

 Bideiis grandiflora (Fig. 119). Of the former I re- 

 ceived, in exchange from botanical gardens, a certain 

 number of packets of seeds from various sources. The 

 contents of the various packets were mixed before sow- 

 ing. This multiple origin showed itself clearly in the 

 number of ray-florets; for the curve expressing their 

 variation was not homogeneous as usual but had two 

 apices (Fig. 118 A). One peak was at 13-14 florets, 

 the other at 21. This must mean that there were two 

 races present, mixed together.^ 



This interpretation was proved to be correct in the 

 following year (1893) when, as a result of choosing 

 seed-parents from one of the supposed races (the 13- 

 rayed one) every trace of the second peak disappeared 

 (Fig. 118 B). It did not appear again in 1894. 



Two-peaked curves occur also in man, and here again 

 they are regarded as the expression of the incomplete 

 fusion of types which have interbred for many cen- 

 turies.^ Such curves have also been observed by Bate- 

 son^ and Weldon* in their important investigations 



* Eine sweigipfelige Variatwnscurve, Roux' Archiv fiir Ent- 

 wickelungsmechanik, II. Band, 1895, P- 52. See also the second 

 volume. 



^Otto Ammon^ Die natilrliche Auslese beim Menschen, 1893. 



^Bateson^ Proc. Zool. Soc, London, 1892, p. 585. 



*Weldon, loc. cit. 



