296 Evolution and Adaptation 



shows the mutations that arose between 1887 and 1899 

 from these plants. The seeds were selected in each case 

 from self-fertilized plants of the lamarckiana form, so that the 

 new plants appearing in each horizontal line are the descend- 

 ants in each generation of lamarckiatia parents. It will be 

 observed that the species, O. oblongata, appeared again and 

 again in considerable numbers, and the same is true for 

 several of the other forms also. Only the two species, O. 

 gigas and O. scintillans, appeared very rarely. 



Thus De Vries had, in his seven generations, about fifty 

 thousand plants, and about eight hundred of these were muta- 

 tions. When the flowers of the new forms were artificially 

 fertilized with pollen from the flowers on the same plant, or 

 of the same kind of plant, they gave rise to forms like them- 

 selves, thus showing that they are true elementary 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, O. scintillans, that appeared eight times, is 

 not constant as are the other species. When self-fertilized 

 its seeds produce always three other forms, O. scintillans, 

 O. oblongata, and O. 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, O. lavifolia, 

 collected in the field, plants were reared, some of which were 

 O. lamarckiana and others O. Icevifolia. They were allowed 

 to grow together, and their descendants gave rise to the same 

 forms found in the lamarckiana family, described above, 

 namely, O. lata, elliptica, nannclla, rubrinervis, and also two 

 new species, O. spatulata and Icptocaipa. 



In the lata family, only female flowers are produced, and, 

 therefore, in order to obtain seeds they were fertilized with 



1 O. 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. 



