Summary

Discusses the connection between climate and vegetation. Believes that an equable climate is unfavourable to increase of species either by importation or modification of existing forms; illustrates his view with reference to particular floras. Hopes to acquire facts to support CD’s idea that isolation is important in producing new forms. Considers the floras of islands some of which do have distinctive species but others of which do not. Agrees that the wide ranges of cryptogams are a consequence of their means of dispersal. Asks for references to works on original creation and species mutability in order to get the best notions of "the (mad) theories of some men from Lamarck’s twaddle upwards".

Summary

Questions on JDH’s sketch comparing floras of Australia, New Zealand, and western S. America; wishes to know botanical relations between other southern islands. Botanico-geographical discussions and comments on books sent by JDH.

Summary

Would like to visit on the weekend of 7–8 December.

Differences in floras of St Helena and Ascension.

Summary

Differences in variability of species within a single genus. Further observations on Lycopodium.

Interested in Humboldt’s river with different floras on opposite banks, and other unexplained cases of very local distributions.

Summary

Acknowledges note and parcel for Ehrenberg.

Considers why different areas have different numbers of species. Gives an example opposing JDH’s view that paucity of species results from vicissitudes of climate. CD has concluded that species are most numerous in areas that have most often been divided, isolated from, and then reunited with, other areas. Cannot give detailed reasons but believes that "isolation is the chief concomitant or cause of the appearance of new forms".

Summary

Remarks on geographical divisions of the flora of the Southern Hemisphere.

JDH beginning Galapagos plants. Value of studying insular floras with respect to inquiries about adaptation of species.