PLANT BREEDING 3821 
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 hybrids. Among the most important examples are the 
genera Oanna, Amaryllis, and Gladiolus. 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 have 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, 
1See Yearbook of the Department of Agriculture, 1904, 
