Summary

Suggests there is a direct relation between temperature and abundance of plant species.

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

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

Sends notes on Infusoria for Ehrenberg.

Comments on distribution of species in natural orders that have local distributions. Intermediate forms between species of Lycopodium.

Summary

Origin of Antarctic brash ice.

Further on case of Lycopodium: does JDH know any genera of plants whose species are variable in one continent but not in another? Discussion on variations between floras as regards species richness, and factors affecting geographical distribution. On species, CD expects "that I shall be able to show even to sound naturalists that there are two sides to the question of the immutability of species; – that facts can be viewed and grouped under the notion of allied species having descended from common stocks". Mentions books and papers for and against species mutability. CD believes past absurd ideas arose from no one’s having approached subject on side of variation under domestication.

Would like to see Clarke’s paper

and would welcome visit from JDH.

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

Would like JDH to visit. Regrets he will not be fit to visit JDH.

Summary

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

Differences in floras of St Helena and Ascension.

Summary

Instructions for JDH’s trip to Down.

Summary

Change in train times.

Summary

Thanks for pleasant stay at Down.

Remarks on boulders found on southern islands.

Describes the alpine character of the Andes flora and relays information on other mountain floras.

Quotes instances of seeds that retained their vitality after being carried by ocean currents.

Sends notes on the comparative floras of New Zealand, Australia, and west coast of South America.

Encloses a copy of part of a letter from George Gardner in Ceylon concerning the European character of the mountain flora.

Summary

Thanks for botanico-geographical remarks. CD greatly appreciates JDH’s valuable generalisations.

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

Thanks for CD’s comments on "sketch".

Lengthy discussion of geographical distribution and island floras.

Has been "delighted with" [Robert Chambers’] Vestiges [of creation (1844)].

Galapagos flora work goes on well.