RaniiHculiis Bulbosiis Sciiiiplcnus. 247 



I conclude, therefore, that in this case the half race 

 cannot be transformed into the double race by simple 

 selection, but only by an internal change — a mutation — 

 the external causes of which are still unknown to us. 



Proceeding now to the detailed description of my 

 experiment, I begin with the half race in the conditions 

 in which I originally found it in nature. 



I found the half race growing in 1886 and 1887 in a 

 sunny and sandy spot not far from Hilversum, where I 

 have often seen it since. The bulbous buttercup grew 

 there in abundance ; most of the flowers were normal, 

 but a considerable number had more than five petals. 

 I shall refer to these latter for convenience of expression 

 as pleiopetalous. 



For several years I have recorded the flowers in that 

 iocality. I give the records of 1886 and 1887, each of 

 which relate to 300-400 flowers. The data are given as 

 percentages. 



The two series^ agree as closely as could be expected 

 and the records for the other years also fall in line. The 

 maximum of the curve (see Fig. 51 H) is over the 

 normal number of petals ; and from it the curve falls 

 rapidly. It is a so-called half GALTON-curve. Flowers 

 with less than five petals do not occur in this locality. 



The great steepness of this curve is due to the fact 

 that on many of the plants no pleiopetalous flowers were 

 found on the days when the observations were made. 

 But this does not mean that the lialf race is mixed with 



^ Uehcr halhe GaUon-Curven ah Zeichcn discontinuirJichcr J^an'a- 

 fioii. Ber. d. d. bot. Gescllschaft, Vol. XI T, 1894. p. 197. where some 

 of the scries of figures ofivcn below can also be found. 



