False Atavism 195 



yellow ones, and from the variety " Delila " 

 of the same species two red ones, a single white 

 and two belonging to another variety called 

 '' Firefly." CalUopsis tinctoria has three va- 

 rieties, the ordinary type, a brown-flowered 

 one and one with tubular rays. Seeds of each 

 of these three sorts ordinarily contain a few 

 belonging to the others. Iberis umbellata rosea 

 often gives some white and violet examples. 

 The '^ Swan " variety of the opium-poppy, a 

 dwarfish double-flowered form of a pure white, 

 contained some single-flowered and some red- 

 flowered plants, when sown from cormnercial seed 

 are said to be pure. But these were only occa- 

 sional admixtures, since after artificial fertiliza- 

 tion of the typical specimens the strain at once 

 became absolutely pure, and remained so for a 

 series of generations, as long as the experiment 

 was continued. Seeds of trees often contain 

 large quantities of impurities, and the laciniated 

 varieties of birch, elder and walnut have often 

 been observed to come true only in a small 

 number of seedlings. 



In the case of new or young varieties, seed- 

 merchants often warn their customers as to the 

 probable degree of purity of the seeds offered, 

 in order to avoid complaints. For example the 

 snow-white variety of the double daisy, BelUs 

 perennis plena, was offered at the start as con- 



