Effect of Selection Obliterated by Nutrition. 



D.-1/ 



in Coriandriim sativum and Madia elcgans selection had 

 decidedly a greater effect (§8). Thus we see that in 

 such experiments selection and nutrition are factors of 

 the same order, and therefore that, in hreeding experi- 

 ments on the effect of one of these factors, the first con- 

 dition, although it is often extremely difficult to fulfil, 

 is that the other factor should be kept perfectly constant. 



The characters whose variation I investigated were 

 the number of rays in the umbels of Ancthiim and Co- 

 riandrum, the number of ray-florets in the heads of 

 Chrysanthemum, Coreopsis, Bidens and Madia. The 

 numbers of these vary pretty considerably, and afford 

 beautiful illustrations of Ouetelet's law,^ as will be seen 

 at the first glance at our figures. For the construction 

 of the curves, the numbers of rays on the terminal umbel 

 or head of the main stem was taken as a measure of this 

 character in the individual in question; no attention was 

 paid to the lateral umbels and secondary heads. Seed 

 was gathered without regard to the qualities of these 

 lateral umbels and heads ; except that those plants whose 

 secondary or tertiary umbels or heads remained too much 

 behind the primary one, were always the first to be rooted 

 out. 



The experiments began in the spring of 1892. The 

 seed for sowing was obtained either from nursery-men 

 or from botanical gardens {Chrysanthemum). It must 

 therefore have been obtained from moderatel}' manured 

 cultures, and was sown by me in rich but not too heavily 

 manured soil, in the open. During the three years of the 

 experiment the manuring and other treatment was uni- 

 form. The manure was the same as that which was 



'^Ber. d. d. hot. Ges., Bd. XII, 1894, p. 200. {Coreopsis and Anc- 

 thum). 



