The collection consists of two series:

Letter from Nathaniel Wallich to Professor Henslow (Botanist on Indian plants) concerning specimens that Wallich is sending to him. He asks to be remembered to Mrs Henslow and remembers with gratitude their hospitality and treatment among the Professors at Cambridge. He asks that Henslow tell Professor Sedgwick that he has written to his friend Mr J Calder at Calcutta concerning the Poona Apophallite. Handwritten, dated 17 November 1831

Letter from Henry Thomas Colebrooke to "My dear Lord". Acting in his role of President of the Asiatick Society (role held from 1806--1815) he was requesting that the Lord, as Patron, would act to enable Dr Wallich, keeper of the Society's museum to continue at the Presidency rather than be sent to his recent appointment at an outstation. Handwritten, dated 19 October 1814 from Calcutta. Appended to this letter is a copy of a note written by Wallich about his debt to Colebrooke in obtaining his position at the Calcutta Garden. Handwritten, dated 15 October [1820]. This has further handwritten annotation stating that "The following... Extract from letter of Dr Wallich to Dawson Turner and is in the handwriting of the latter."

Letter from Henry Thomas Colebrooke to Nathaniel Wallich asking for him to supply botanical information in order for him to complete a publication on Indian plants. The letter includes a list of the information that he needs. He also asks for information about certain teak plantations. Handwritten, dated April 1817 from Albany London, with mention of Lord Castlereagh, 4 September in Wallich's hand (Boat on which the letter arrived).

Letter from Henry Thomas Colebrooke to Nathaniel Wallich acknowledging letters sent and stating that he has sorted Wallich's remittances and arranged for the periodicals he requests to be sent to him. He was pleased with the geological specimens sent to him, including gold from Tartary and specimens from Lieutenant Gerard and Mr Scott and Colebrooke has used the notes sent by Gerard to write a paper on the geology of the valley of the Sutlej. He has proposed Lt Gerard and Dr Jack as members of the Geological Society. He thanks Wallich for seeds sent but advises because of the cost to be careful in thinking through which to send. Handwritten, dated 9 January 1821, received 5 June 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he thanks Wallich for his correspondence and his Geological and Botanical Despatches and for Mr D Scott's remarks. He enquires whether Scott would like to be a member of the Geological Society. He writes of Limestone specimens that Wallich sent and of that he is pleased that the Gayal cattle have not been sent. He suggests that Wallich might write to his relative, Mr James Gosling, at the Cape of Good Hope who would be happy to try any specimens in his garden that Wallich thinks could flourish there. He asks about various species and botanical drawings. Handwritten, dated 8 September 1819, received 16 March 1820.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which Colebrooke discusses the periodicals that are being sent and how much the remittance will cover. He writes that he has just learnt, with regret of the death of Dr Jack. Handwritten, dated 8 January 1823, received 17 June, 1823.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he discusses the possibility of the introduction of rice to England. Colebrooke thanks for letters, boxes of specimens and anthropological drawings. Colebrooke asks Wallich to express his thanks to the gentlemen that provided geological specimens. Colebrooke has petitioned the Chair of the Court of Directors, East India Company on Wallich's behalf. He wishes Wallich a speedy recovery to health. Handwritten, dated 8 August 1820, received 25 February 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich concerning Wallich's concern on sending specimens to India House and publications to be sent to Wallich from Richardson. There is a postscript in which Colebrooke reports that Law desires to be remembered to Wallich, that the plants have been given to the Horticultural Society and the seeds given to the Court of Directors to distribute among their friends, However, generally, Indian seeds do not germinate in England. Handwritten, dated 6 November 1823, received 31 May 1824.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he congratulates Wallich for his success in research in Nepal. Colebrooke discusses publications to send to Wallich. He again reiterates the need to send specimens directly to such institutions as the Linnaean and Geological Societies rather than to him personally. Handwritten, dated 31 July 1822, received 1 February 1823.