All experience favors the belief that such violent crosses as wheat with rye, raspberry with blackberry, peach with plum, or our native wild crab with the cultivated apples, will not give results of value. Without doubt some of these violent crosses can be made, but the writer's experience has been that the seeds were either abortive or only capable of making a weak growth. It has been claimed that hybrids have been developed by crossing the blossoms of our wild crab (Pyrus coronaria) with pollen of the common apples. On the college grounds at Ames on several occasions such crosses have been made with great care by only pollinating the first blossoms that opened on the Soulard and wild crab. That a cross was secured is evidenced by the fact that the shape, color, and cavity were changed in the crossed apples. Where the Soulard was crossed with Roman Stem pollen even the fleshy protuberance at the base of the stem of the latter variety was reproduced in the Soulard crab. But not a single perfect seed was found in over one hundred specimens.
In some cases the near relation of two species can only be determined by trial. As an instance, the blossoms of Pyrus Toringo - which is a mere bush with fruit not much larger than a pea - were crossed with pollen of Oldenburg apple. The resulting hybrids were upright and tree-like in habit, with much enlarged leaves, and unexpectedly the fruit yielded enlarged and perfect seed. The size of the fruit was not larger than a small Siberian crab. In this case repeated crossings may give winter apples of real value and of fair size for market.