PLANT BREEDING 321 



Agriculture, under the direction of Dr. H. J. Webber.^ 

 The hardy trifoliate orange, which resists our winters as 

 far north as Philadelphia, but bears a small, bitter, worth- 

 less fruit, was hybridized with the common sweet orange. 

 Three valuable hardy hybrids known as citranges were pro- 

 duced. One of them makes a good substitute for grape- 

 fruit, another for lemons, and the third for rather sour 

 oranges. They may be grown from two hundred to four 

 hundred miles farther north than ordinary oranges. 



Another citrous hybrid is that between the tangerine 

 and the grape-fruit. This is called the tangelo (Fig. 224) 

 and has characteristics somewhat intermediate between 

 those of the parent species. It is smaller in size, and the 

 pulp is less bitter and acid than that of the grape-fruit, 

 while the " kid-glove " skin, readily peeled off with the 

 fingers, is like that of the tangerine. 



401. Results of Hybridizing Ornamental Flowers. — Some 

 of the most showy flowers of our gardens and greenhouses 

 are hj'brids. Among the most important examples are the 

 genera Canna, Amaryllis, and Grladiolus. Orchids, too, have 

 been hybridized to such an extent that a dictionary of hy- 

 brid orchids has been prepared. 



In most cases of flowers which have been bred and 

 hybridized for many years the process of improvement has 

 been due partly to crossing and partly to selection. It is 

 often impossible to find, out how many parent species or 

 varieties ha^'e entered into the production of the final 

 hybrid. 



402. Summary of Methods and Results. — Successful 

 plant breeding requires a continuous effort to get better 

 plants, either by picking out and growing chance varieties, 



1 See Yearbook of the Department of Agriculture, 1904. 



