THEORY AND PRACTICE 



the dooryard than to work with reference to the 

 modification of the color of the flowers. 



There are numerous familiar plants with any 

 one of which you might work to advantage, f or 

 example, the gladiolus, the dahlia, the verbena, or 

 the nasturtium. All of these plants show great 

 color variation. In cross-breeding and selecting 

 to secure new combinations of color, you are deal- 

 ing with a restricted group of hereditary factors, 

 and hence it will not be necessary to have large 

 numbers of individual plants. Moreover, color in 

 flowers is a new or recent development in the evo- 

 lutionary sense, and hence modifications of color 

 are more readily brought about than changes of 

 root or stem or leaf. 



It is probable that all flowers were originally 

 green, and that in the course of evolutionary de- 

 velopment some flowers changed from green to 

 blue and then to indigo and violet, while others 

 ran the chromatic scale in the other direction, 

 varying from green through yellow and orange 

 to red. Eed and violet flowers are therefore prob- 

 ably new in the evolutionary sense, blue and yellow 

 flowers being old. White flowers may be due to 

 having air in their cells, or to the blending of other 

 colors say yellow and blue. Yellow flowers may 

 be due to the blending of red and green. In 

 general, the mixture of factors for color in the 

 heredity of a flower may rival in complexity the 

 mixture of pigments on the canvas of an artist. 



The greatest interest of all, perhaps, for the 

 amateur plant developer, attaches to the bringing 



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