( 



318 A TEXTBOOK OF BOTANY [Ch. VI, 9 



not for our historical records. Most remarkable of all, and 

 perhaps the acme of man's developmental accomplishments, 

 is the Chrysanthemum, in which, from two little simple 

 wild plants, smaller than our common field Daisies, have 

 been developed all of the great variety of distinct types, and 

 all of the superb individual specimen plants seen in our 

 horticultural exhibitions, culminating in single plants over 

 sixteen feet across and bearing fifteen hundred blossoms, and 

 in single blooms over twenty inches in diameter. We 

 consider now the methods by which man has achieved 

 these results. 



New varieties originate under cultivation, but not as a 

 direct result thereof. High cultivation can supply the con- 

 ditions for the best development of individual plants or a 

 given crop, but the improvement is not hereditary, and 

 therefore does not yield new kinds, which we acquire in only 

 three ways, — by selection of variations, preservation 

 of sports, and hybridization. 



1. Selection of variations. Both experience and experi- 

 ment attest that plants of the same variety growing side by 

 side, whether wild or in gardens, present many differences, 

 or variations, from one another ; further, that some of these 

 variations are hereditary, though many are not; and still 

 further, that by persistent selection generation after gen- 

 eration of the plants displaying a given variation {e.g. size 

 in a grain, red color in a flower) , and the use of their seeds 

 in growing the next crop, there results in time a variety in 

 which the given feature is far more prominent and prevalent 

 than in the original form, and moreover comes true to seed. 

 It is true that much of such selection now practiced upon 

 highly developed varieties of plants, whether grains or flowers, 

 appears to consist simply in the assembling together of the 

 plants which already possess the variation in high degree, 

 and is not accompanied by any actual intensification 

 thereof. In other words, selection may effect the isolation 

 rather than the development of a variety. But an intensifi- 



