166 Obscri'Litioii of the Origin of raricfics. 



to be avoided on account of the sterility of the most 

 highly modified individuals. 



My cultures embraced, as a rule, a hundred indi\'id- 

 uals each, but sometimes a few hundreds. There can 

 hardly be a doubt that if I had carried out more extensive 

 sowings I should have attained my object at least one 

 year earlier. But the more stringent the selection is, the 

 smaller are both the harvest and consequently the next 

 year's crop. 



Of course the reader will ask, has this transition been 

 a gradual or a sudden one ? I consider it sudden ; but 

 much depends on the meaning that we attach to the 

 w^ords. At any rate the change did not occupy centuries, 

 as is comnionly supposed by the current theory of selec- 

 tion; it did not even require one decade. Three years 

 were sufficient in a culture of no more than a few square 

 meters in extent. 



I now come to the details of the experiment and shall 

 first give a short description of the original wild species. 



The species does not grow around Amsterdam. The 

 herbarium material collected by me in various parts of 

 the Netherlands points to the general occurrence of a 

 mean number of 13 rays. Heixsius plotted curves from 

 plants from two localities in the province of North Bra- 

 bant, and obtained the following numbers. The first row 

 relates to plants which were collected near Vucht, the 

 second to a collection from Hintham.^ 



NUMRER OF LIGULATE FLORETS (l. F.) IN THE NETHERLANDS, 



L. F. 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 



Vucht 1 13 5 3 8 18 78 37 22 11 17 2 3 3 



Hintham 10998 15 14 33 94 101000 



^ Bcr. d. d. hot. Gcs., Vol. XVII, p. 87. 1 have already exhihited 

 the variation in hoth localities united into a single curve in Vol. I 

 (See p. 152, Fig. 2,2). 



