Professor Bailey says in his book on "Plant Breeding": "It is necessary, on account of the indefiniteness of the term 'variety, to remember that only varieties true to seed, or races and sub-species, can bequeath their characteristics with any degree of certainty; inconstant species often designated as varieties are not considered in the theory of hybridization."
The development by crossing and selection of our native grapes, strawberries, blackberries, raspberries, and gooseberries has been quite rapid and satisfactory, but much remains yet to be done. The possibilities are shown by one test with the gooseberry. The blossoms of the wild species of Manitoba were pollinated with the pollen of Champion and Industry; over one hundred seedlings resulted, all of which were more vigorous than the wild species, with larger, thicker leaves, and some of them bear fruit as large as the Champion. Other indigenous fruits are as yet neglected, such as the sand-cherry (Prunus pumila), the dwarf Juneberry, and possibly the huckleberry.
In the mild and relatively equable parts of the earth the orange, lemon, citron, banana, date, fig, guava, loquat, persimmon, and even pineapple, have been developed so far by culture and selection. So far as known no attempt has been made to improve any of them by crossing or hybridizing. Judging by advances made with other fruits it would prove valuable work to cross the Japan persimmons with our native species, the St. Johns River oranges with the hardy, rather dwarf types of north Japan, the common figs of the South with the best varieties from Smyrna, the common mission date palm of Arizona with the best grown in Algeria. Still other lines of profitable crossing will occur to the mind, especially in Cuba, Porto Rico, and Mexico.