Read before the American Association for the Advancement of Science, at St. Louis, August 1878.

The author shows that hybrid plants must be rare in nature, for the following reasons, which with the experiments and observations on which they are founded, were given in detail:

1st. Intermediate forms are thought to be hybrids, because they are intermediate; but actual experiment rarely results in intermediate forms.

2nd. Hybrids, when fertile, rarely reproduce their exact forms from seed.

3rd. Hybrids could not therefore spread themselves over large districts and preserve their identity.

4th. The same two parent species rarely produce the same hybrid form though the flowers be from the same two plants, and though the act of crossing be performed at the same time; therefore identical forms in distant places if of hybrid parentage, could scarcely have spread from one original, if at all.

5th. The wide distribution of some supposed hybrids, must therefore imply a remote origin in geological time, not well harmonizing with their supposed beginning between modern species.

6th. The facts connected with supposed hybrids in nature are more consistent with the theory of innate and sudden evolution of forms, as propounded by the author in former papers before the association.