108 Plant-Breeding 



garden. The two stocks would then intercross, with a 

 thorough blending of their whole organizations, and with 

 no loss of purity to the variety, and this would yield far 

 more favorable results than a mere change of seed." 



CROSSING FROM STANDPOINT OF PLANT IMPROVEMENT 



The making of crosses for man's use may have a very dif- 

 ferent meaning from the effect of crossing upon the plant 

 itself. Man removes from a plant by cultivation most of 

 the factors which make for struggle and determines whether 

 the plant shall survive or not. In making crosses or 

 hybrids with a practical object in view, the welfare of the 

 species is taken into account only sufficiently to insure 

 vigorous plants particularly adapted to man's purposes. 



Understanding of terms. At this point it is worth 

 while to consider a few definitions. 



The Latin word hybrida, or ibrida, has been assumed to be 

 derived from the Greek v/fyus, an insult or outrage, and a 

 hybrid has been supposed to be an outrage on nature, an un- 

 natural product. The term hybrid is by many applied only 

 to the offspring obtained by crossing two plants or animals 

 sufficiently different to be considered by naturalists as 

 distinct species, while the term cross is used to designate 

 the offspring of two races or varieties of one species. A 

 closer scrutiny of the facts, however, makes the term 

 hybridism less isolated and more vague. The words 

 species and genera, and still more sub-species and varieties, 

 do not correspond with clearly marked botanical categories, 

 and no exact line can be drawn between the various kinds 

 of crossings from those between individuals apparently 

 identical to those belonging to genera universally recog- 



