Production of Double Flowers 495 



individuals with the lesser degrees of deviation. 

 Now the marigold averages 13, and the 

 grandiflorum 21 rays. The wild species is pure 

 in this respect, but the garden-variety is not. 

 The seeds which are offered for sale usually 

 contain a mixture of both forms and their 

 hybrids. So I had to isolate the pure types 

 from this mixture and to ascertain their con- 

 stancy and mutual independency. To this end 

 I isolated from the mixture first the 13-rayed, 

 and afterwards the 21-rayed types. As the 

 marigolds are not sufficiently self-fertile, and 

 are not easily pollinated artificially, it seemed 

 impossible to carry on these two experiments at 

 the same time and in the same garden. I de- 

 voted the first three years to the lower form, 

 isolated some individuals with 12 - 13 rays out of 

 the mixture of 1892 and counted the ray-florets 

 on the terminal head of every plant of the en- 

 suing generation next year. I cultivated and 

 counted in this way above 150 individuals and 

 found an average of exactly 13 with compara- 

 tively few individuals displaying 14 or only 12 

 rays, and with the remainder of the plants 

 grouped symmetrically around this average. I 

 continued the experiment for still another year 

 and found the same group of figures. I was 

 then satisfied as to the purity of the isolated 

 strain. Next year I sowed a new mixture in 



