Well, if you'd like to make a cross in unchartered territory, a mix of two or three pollens will sometimes provide one (mentor) that is compatible. The compatible mentor then, may 'open the door' for your selected pollen to follow. Leaving the stigma unprotected beforehand follows the same thought--that a few acceptable stray grains may enter the stigma and excite it enough so to allow a wider range of otherwise normally incompatible pollen to follow. In thinking, one could end up with a wide range of crosses, but still end up with many of one's intended target. I know of someone in Europe who works the same methods as Dr. Bergman.
