Summary

Thanks AG for 2d part of "Statistics [of the flora of the northern U. S.", Am. J. Sci. 2d ser. 22 (1856): 204–32; 2d ser. 23 (1857): 62–84, 369–403].

Is glad AG concludes species of large genera are wide-ranging, but is "riled" that he thinks the line of connection of alpine plants is through Greenland. Mentions comparisons of ranges worth investigating.

Believes trees show a tendency toward separation of the sexes and wonders if U. S. species bear this out. Asks which genera are protean in U. S.

Summary

Urges AG to generalise from his observations on the flora of the northern U. S.

Expected to find separation of sexes in trees because he believes all living beings require an occasional cross, and none is perpetually self-fertilising. The multitude of flowers of a tree would be an obstacle to cross-fertilisation unless the sexes tended to be separate.

The Leguminosae are CD’s greatest opposers; he cannot find that garden varieties ever cross. Could AG inquire of intelligent nurserymen on the subject?

Thanks AG for information on protean genera; much wants to know whether their great variability is due to their conditions of existence or is innate in them at all times and places.

Summary

Thanks for new part of "Statistics".

Interested in disjoined species; do they tend to belong to large or small genera, and are they generally members of small families?

Is glad AG will tackle introduced plants; has noticed that the proportion of a particular family to the whole flora tends to be similar in introduced and indigenous plants.

Summary

Thanks for AG’s remarks on disjoined species. CD’s notions are based on belief that disjoined species have suffered much extinction, which is the common cause of small genera and disjoined ranges.

Discusses out-crossing in plants.

Has failed to meet with a detailed account of regular and normal impregnation in the bud. Podostemon, Subularia, and underwater Leguminosae are the strongest cases against him.

Summary

Believes species have arisen, like domestic varieties, with much extinction, and that there are no such things as independently created species. Explains why he believes species of the same genus generally have a common or continuous area; they are actual lineal descendants.

Discusses fertilisation in the bud and the insect pollination of papilionaceous flowers. His theory explains why, despite the risk of injury, cross-fertilisation is usual in the animal and vegetable kingdoms, even in hermaphrodites.

Summary

Encloses an abstract of his ideas on natural selection and the principle of divergence; the "means by which nature makes her species".

Discusses varieties and close species in large and small genera, finding some data from AG in conflict with his expectations.

Has been observing the action of bees in fertilising kidney beans and Lobelia.

Summary

Thanks AG for his criticisms of CD’s views; finds it difficult to avoid using the term "natural selection" as an agent.

Discusses crossing in Fumaria and barnacles.

Has received a naturally crossed kidney bean in which the seed-coat has been affected by the pollen of the fertilising plant.

Finds the rule of large genera having most varieties holds good and regards it as most important for his "principle of divergence".

Summary

Discusses the ranges of alpine species in U. S. and considers the possible migration routes of such species from Europe.

Lists those U. S. genera which he considers protean and describes the U. S. character of some genera which are protean in Europe.

Describes how he distinguishes introduced and aboriginal stocks of the same species.

Summary

Comments on species with disjoined ranges; does not feel, despite CD’s expectations, that they tend to belong to small families.

Gives the proportion of U. S. trees in which the sexes are separate [see Natural selection, p. 62].

Summary

Discusses difficulties involved in deciding which genera are protean in the light of some comments by H. C. Watson.

Summary

Believes, with CD, that extinction may be an important factor in explaining plant distributions, but sees no reason why the several species of a genus must ever have had a common or continuous area. "Convince me of that, or show me any good grounds for it … and I think you would carry me a good way with you". It is just such people as AG that CD has to satisfy and convince.

Feels that the crossing of individuals is important in repressing variation and perhaps in perpetuating the species, but instances some plants in which it cannot, apparently, take place.

Summary

States he has "misgivings about the definiteness of species". Believes there is some inherent tendency for plants to originate varieties. Cross-fertilisation is likely in most cases but sees difficulties with plants like Adlumia.