84 Plant-Breeding 



purea), and in gloxinia. Many other instances of peloric 

 flowers are on record, which indicates that pelorism as a 

 mutation is frequent. 



Experimental study of the origin of mutations. De Vries 

 has conducted a series of experiments for the purpose of 

 observing the origin of mutations, if any should occur. 

 One of the plants chosen for these studies was the peloric 

 toad-flax (Linaria vulgaris peloria). The most accurate 

 laboratory methods were applied. The plants were 

 carefully isolated }n his garden. 



The reason for this choice of the peloric toad-flax lay 

 in the fact that this form is known to have originated 

 from the ordinary type at different times and in different 

 countries under more or less divergent conditions. The 

 ordinary toad-flax bears exceedingly unsymmetrical 

 flowers. (See Fig. 23, A.) But symmetrical flowers are 

 not uncommon in such plants as the toad-flax and snap- 

 dragon, which have similar types of flowers. In these 

 experiments, de Vries sought to observe the birth of this 

 anomaly in his pedigree cultures. 



The experiments were begun in 1886 with normal 

 plants ; a few peloric flowers were produced, however, 

 which is not an uncommon occurrence among plants of 

 this genus. Throughout the next few generations, 

 nothing more than the normal number of peloric flowers 

 were produced. 



In the third generation, among the many thousands of 

 flowers there occurred one having five spurs. This was 

 inbred by hand and produced a considerable quantity of 

 seed. All other seed was discarded and this plant now 

 became the parent of all future plants. 



