Introduces Theodore Lyman of Boston, Massachusetts, who is coming to Europe for second time to meet "the most distinguished literary characters". Encloses account of the "great 'Lycoperdon' of South Carolina" from information given by James Macbride, who is now a FMLS. Hosack's pupils are collecting the plants of New York, an account is being prepared which will be sent to Smith or Linnean Society.

Apologises for long silence since he saw Smith last summer; thanks for the honorable treatment given to his son [Karl Heinrich Mertens] and compliments Lady Smith.

Has dedicated his history of botany to Smith ["Anleitung zum grundlichen Studium der Botanik"]. He has written it as an up to date version of [Kurt] Sprengel's similar work, but in German rather than Latin. [Johann Jacob] Römer [(1763-1819), Swiss physician and botanist] to send Smith first volume of their new edition of Linnaeus' "Systema vegetabilium"; remarks on the increase in sheets needed to take in new discoveries and explains some of the plan. Has been asked to translate Smith's "Introduction to Physiological and Systematical Botany"; asks if there any remarks he would like to add. Offers to send alpine seeds.

Informs Smith he will be at Spring Grove, Isleworth, Middlesex, for a while and encloses £6 for supply of turkeys.

Working with Johann Wilhem Meigen [(1764-1845), German entomologist] on 'Diptera' [flies] and updating his 1804 work ["Die Fliegen"], correcting the Fabrician synonymy by comparing against the collections of [Johan Christian] Fabricius. Asks for Smith's assistance by facilitating comparison with Linnaean collections, by either specimens or drawings and descriptions. Proposes [William Elford] Leach as an alternative.

[On separate folio] List of dubious species.