62 Plant-Breeding 



large and of a bright yellow color, attracting immediate 

 attention, even at a distance. They open towards 

 evening, as the name indicates, and are pollinated by 

 bumble-bees and moths. On bright days their duration 

 is confined to one evening, but during cloudy weather they 

 may still be found open on the following morning. Con- 

 'trary to their congeners, they are dependent on visiting 

 insects for pollination. 



" In CE. Lamarkiana no self-fertilization takes place. 

 The stigmas are above the anthers in the bud, and as the 

 style increases in length at the time of the opening of 

 the corolla, they are elevated above the anthers and do 

 not receive the pollen. Ordinarily the flowers remained 

 sterile if not visited by insects or pollinated by myself, 

 although rare instances of self-fertilization were seen." 



(E. Lamarkiana is a biennial, producing rosettes in 

 the first year and stems in the second year. This species 

 was found to be variable in all periods of its life cycle, 

 in the seedlings, the rosettes, and the stems. 



De Vries pursued three methods in obtaining his muta- 

 tions : 



1. Observations and studies of the plants while growing 

 in the wild state in the fields. 



2. Some of the plants were removed from the wild state 

 and placed under cultivation. Many of the plants were 

 self -fertilized and their seed sown under controlled con- 

 ditions. By this method several mutants were found 

 which were too weak to withstand the competition of field 

 conditions. 



3. Repetition of the sowing process for several genera- 

 tions, leading to the production of new forms. 



