316 Plant Life and Evolution 



the vivid orange-yellow California poppy he has de- 

 veloped a bright red variety by selecting individuals 

 which showed traces of red in the petals, and then 

 by successive selection of the offspring, the red color 

 was intensified until a pure red flower resulted. 

 Similar examples of such selections can be shown 

 in the development of many cultivated plants, and 

 thus it is proved that under certain conditions, at 

 least, selection alone is sufficient for the origin of 

 new forms. Whether or not natural selection is 

 the usual form of the origin of new species, there 

 can be little doubt that it is an essential factor 

 in maintaining the new form after it has once 

 appeared. 



LAMARCKISM 



Modifications in Cultivated Plants Due to 

 Changed Environment. No student of plant-be- 

 havior can doubt that the structure of the plant is 

 readily affected by its environment. Changes in the 

 environment are quickly reflected by changes in the 

 structure of the plant. As we have already con- 

 sidered this at some length in a former chapter, the 

 matter will not be enlarged upon here. The ques- 

 tion naturally arises: Are the ontogenetic changes 

 due to enviroment capable of transmission ? To this 

 the experimenter answers at once, They certainly are. 

 Striking instances of this are the numerous cases 

 of acclimatization. Races of domestic plants, e.g., 



