Summary

CD encloses letter from Asa Gray, although it is critical of JDH.

Role of struggle in forming species in retreat from advancing glaciers.

Summary

Variability of naturalised plants.

Distribution of Arctic/alpine plant species.

Limits to the northern range of plants.

Summary

Asks whether Allegheny Mountains are sufficiently continuous so that plants could travel from north to south along them.

Hopes AG’s work on geographical distribution is progressing, as he has questions on plants common to Europe which do not range up to Arctic.

Are intermediate varieties less numerous in individuals than the varieties they connect?

Summary

Outlines the ranges of northern U. S. species common to Europe. Hopes to investigate the resemblances between the floras of the north-eastern U. S. and western Europe. Discusses routes by which alpine plants appear to have reached U. S.

Summary

Thanks AG for the first part of his "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]

and for information on social and varying plants.

Would like to know number of genera of introduced plants in U. S.

Is surprised at some affinities of northern U. S. flora and asks for any climatic explanations.

Asks what proportion of genera common to U. S. and Europe are mundane.

Is glad AG will work out the northern ranges of the European species and the ranges of species with regard to size of genera.

Summary

Rarity of intermediate varieties.

Variability of introduced plants.

Ranges of plants common to Europe and U. S.

Summary

Continued debate on formation of species as a result of retreat from glaciers.

JDH suggests internal powers of species modification, which he knows CD abhors.

Summary

Plants that are social in the U. S. but are not so in the Old World.

Distribution of U. S. species common to Europe.

Gives Theodor Engelmann’s opinion on the relative variability of indigenous and introduced plants and notes the effects of man’s settlement on the numbers and distribution of indigenous plants.

Summary

Can no longer make out story of NW. American plants; consulting Asa Gray.

Questionable validity of seed-salting experiments.

Aristolochia and Viscum seem to shed pollen before flower opens.

Ray Society should only do translations.

Thomas Thomson in India has rediscovered Aldrovanda, a rare relative of Drosera.

Summary

CD’s predicament with continental extensions: they would remove argument for multiple creations, yet he opposes the doctrine. Lyell will not express an opinion on this.

Lyell fears mutability would lead to more specific names.

Encloses copy of letters to Lyell [1910 and 1917].

Summary

Agassiz has informed him that the mice and rats of Mammoth Cave are American in type.

Alludes to CD’s doubt of the principle that "progress of life on the globe is parallel with the development in different tribes". Outlines his own ideas on the "unfolding of the type-idea" and its "parallelism with the law of development in the embryo".

Summary

Answers CD’s questions about plants common to U. S. and Britain and their distribution in Europe.

Variability of agrarian weeds.

Summary

Thanks for sending paper on geological development (Dana 1856). Discusses infertility of species. Discusses first part of Asa Gray’s paper (A. Gray 1856–7). Thanks for note on the Cave Rat. Discusses a new species of fossil cirripede, in the genus Chthamalus. Explains his interest in pigeon breeding.

Summary

Suggests affinities of the U. S. flora that he considers would be worth investigating. Wants to know the ranges of species in large and small genera.

Questions AG on naturalised plants; whether any are social in U. S. which are not so elsewhere and how variable they are compared with indigenous species. Would like to know of any differences in the variability of species at different points of their ranges and also the physical states of plants at the extremes of their ranges.

Summary

Conveys [? J. T. I. Boswell-]Syme’s opinion of variability of agrarian weeds and ranges of species common to U. S. and W. Europe. The Hispano-Hibernian connection.

Summary

Believes intermediate varieties are generally less numerous in individuals than the two states that they connect.

Discusses the difficulties of deciding what is the typical form of a species

and gives some opinions on the variability of introduced species compared with indigenous species.