Hayes and Garber - Cucurbit Breeding

262 BREEDING CROP PLANTS
varieties gave good results when introduced into the United
States, the breeding of apples has not been seriously undertaken
until comparatively recent times. The cultivated varieties are
very numerous. Our pears were developed from two very different
wild species, Pyrus communis, the wild pear of western
Asia and Europe and the hard, gritty sand pear of northern China.
P. communis is the source of our eating pears, such as the
Bartlett, while inter-species crosses furnished our cooking and
winter pears.
Peaches were first developed in China. When one compares
the little hard, bitter wild peach of China and our cultivated
varieties the results of early breeding are strikingly illustrated.
There are three groups which are commonly accepted as the
ancestral forms of our cultivated plums: (1) The thorny wild
European species which produces dark purple fruits about the
size of a pea. These are the source of our prune varieties. (2)
North American native wild plums which have a very juicy
flesh without much meat. Several species are recognized
(Wight, 1915). (3) A Chinese-Japanese wild species. Many of
the cultivated varieties of plums are largely of hybrid origin.
There are over 120 wild species of cherries which are native to
Asia and from 200 to 1,500 wild species of raspberries and blackberries.
The variation in type of the wild red raspberries of
New England is a good illustration of a wide diversity of forms.
Some .of these are probably results of crosses with escaped cultivated
varieties.
Natural hybridization certainly played a large
part in the evolution of such fruits and the selection of promising
wild seedlings furnished the major part of our cultivated
varieties.
Fletcher (1916) has described 1879 varieties of strawberries
which originated in North America and 26 European varieties
which have attained prominence in this country. The strawberry
is largely a hybrid product of four or more species.
The citrus fruits are all of Asiatic origin. Present cultivated
varieties have for the most part been produced during the last
100 years. The grapefruit industry of the United States has
been developed in the last 25 years. This fruit, which is a native
of islands lying to the south of Asia, was introduced into the West
Indies early in the eighteenth century and more recently from
the West Indies into Florida.
Table LXVI1, which is part of a table
published by White (1916), is a summary statement of the source