Having obtained a first hybrid generation, he allowed the hybrids to self-fertilize, and recorded the result in a large number of instances (a thousand or more) as to the number of individuals in the first, second, third and fourth generations in which the character selected for experiment made its appearance.
Hybrids are also common, the canary breeding freely with the siskin, goldfinch, citril, greenfinch and linnet.
The hybrids thus produced are almost invariably sterile.
Osaria, auxaria, a bundle of osier or willow twigs), the common term under which are included the various species, varieties and hybrids of the genus Salix, used in the manufacture of baskets.
The occurrence of hybrids in nature explains the difficulty experienced by botanists in deciding on what is a species, and the widely different limitations of the term adopted by different observers in the case of willows, roses, brambles, &c. The artificial process is practically the same in hybridization as in cross-fertilization, but usually requires more care.