VARIATION AND MUTATION 



159 



the flowers on the same plant, or of the same kind of plant, they gave 

 rise to forms like themselves, thus showing that they are true elemen- 

 tary species. 1 It is also a point of some interest to observe that all 

 these forms differed from each other in a large number of particulars. 

 "Only one form, 0. scintillans, that appeared eight times, is not 

 constant as are the other species. When self-fertilized, its seeds pro- 



FIG. 97. At left, section of chestnut, Castanea vesca, showing unusual variations; at 

 right, a branch of Mercurialis annua, which presents several variations. (After 

 de Vries.) 



duce always three other forms, 0. scintillans, 0. oblongata, and 0. 

 lamarckiana. It differs in this respect from all the other elementary 

 species, which mutate not more than once in ten thousand individuals. 

 From the seeds of one of the new forms, 0. Icevifolia, collected in 

 the field, plants were reared, some of which were 0. lamarckiana, and 

 others 0. Icevi/olia. They were allowed to grow together, and their 

 descendants gave rise to the same forms found in the lamarckiana 



1 0. lata is always female, and cannot, therefore, be self-fertilized. 

 When crossed with O. lamarckiana there is produced fifteen to twenty per 

 cent of pure lata individuals. 



