Luther Burbank: Methods and Discoveries 4: 138-140 (1914)
I have hybridized the pear and the apple; also the pear and the quince. The seedlings from these unions have sometimes seemed thrifty, but were always infertile. They were highly interesting none the less.
The most successful cross was obtained by using the pollen of the Bartlett pear upon the Gravenstein apple.
The seedlings from this cross were divergent in appearance, and variable as to growth. One of the seedlings grew fully as fast as the ordinary apple seedling, but most of them had a sickly, dwarfed appearance, and some died after having made a foot of growth. Three or four of those that lived were grafted on an apple tree. They maintained moderate growth for several years, but were never healthy or vigorous, and never gave any intimation of blooming.
The results of the crosses between the pear and quince were closely similar. From these hybrids also I failed to secure fruit. Some grew with great vigor for years, while others almost refused to grow at all. In general appearance, and especially in foliage, the hybrids bear a closer resemblance to the pear than to the quince. But many appeared to be fairly good composites of these widely differing plants.
As there are many varieties both of pears and quinces, each having individual characters and diverse hereditary tendencies, an inviting field is open to the careful and patient experimenter in crossing these distinct yet related species. If the right combination can be effected, the results undoubtedly will be profoundly interesting and valuable. Precisely what these results will be, no one can predict. But that new fruits, making most valuable additions to the dietary, may ultimately be thus developed, there is no reason to doubt.