PRODUCTION OF HYBRIDS 501 



in being on the lookout for variations which promise new 

 values. The surer plan is to take seed from a considerable 

 number of parent individuals which possess the desired quality 

 in a high degree, raise plants from each of these, discard plants 

 of this second generation from all parents whose progeny does 

 not excel, and continue selecting from these superior stocks. 

 In this way many characteristics, such as abundant yield, hardi- 

 ness, early ripening, whiteness in the case of flour, increased 

 percentage of sugar in sugar beets, or improved size or flavor in 

 tomatoes may be secured in a few years of careful breeding. 

 This may be called the selection of good parent plants. 



480. Production of hybrids. An important method of mak- 

 ing new varieties is by crossing, or hybridizing, that is, by 

 pollinating the pistil of one species or variety with pollen from 

 another species or variety. The offspring of cross pollination is 

 known as a hybrid. 



The process of crossing two species is comparatively easy. If 

 plum blossoms, for example, are to be hybridized, the operator 

 must gather enough of those from which pollen is to be col- 

 lected, brush or shake off the pollen, and, if necessary, keep it 

 in a cool place until needed. 1 Most of the flower buds are 

 removed from the tree the flowers of which are to be pollinated, 

 and just before the opening of those buds which are left the 

 corolla, with its attached anthers, is cut away, as shown in 

 Fig. 375, and pollen applied to the stigmas with a camel's-hair 

 pencil or, better, with the finger tip. If fertilization results, 

 and plums with good seeds are produced, they must be planted, 

 and seedling trees grown from them. These might be allowed 

 to grow until they blossomed, but years of valuable time can 

 be saved by grafting the young seedlings upon other plum trees. 

 When blossoms of the hybrid form are secured, some of them 

 may be fertilized with pollen of either of the parent species, 



i Some kinds of pollen, as that of the pansy and the peony, are said to 

 remain good for weeks, and that of the date palm for more than a year; but 

 in general, pollen should be used as soon as possible. 



