The series consists of 38 letters from Joseph Dalton Hooker to Brian Houghton Hodgson. They have been organised mainly according to a previous listing made of the material, approximately by date.

"H.T. Colebrooke - Memoirs and Autographs", A red calf bound book, containing printed and handwritten material including biographical material concerning Colebrooke, obituary notices for Horace Hayman Wilson, and correspondence from Colebrooke to Nathaniel Wallich. On the inside cover there is a bookplate with "Ex Libris Frederick Hendricks, F.S.S., F.S.A., Knight of Vasa. 1893" and a printed auction listing "226. Colebrook (H.T.) Notice historique sure la vie et les ouvrages de M. Colebrooke par M. C.A. Walckenaer, Paris, 1848, with biographical notices from various periodicals and numerous interesting autograph letter of Colebrooke, half red calf". Frederick Hendricks is an ancestor of the donor who also has family connections with the Colebrooke family.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich concerning publications that Colebrooke will forward to Wallich. He reiterates his request to send specimens direct to the Geological Society because of the cost incurred at the Custom House. Handwritten, dated 12 March 1821, received 30 August 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which Colebrooke thanks Wallich for his correspondence and the seeds he has sent. The one that Wallich has sent for the Botanic Garden at Copenhagen he has given to Dr Fleming to take. Colebrooke encourages Wallich to write to Fleming as Fleming was instrumental in Wallich keeping his position at the Botanic Garden. He reiterates his desire for Wallich to send living plants. Colebrooke also thanks Wallich for geological specimens and gives instructions as to how to package them correctly. Wallich has been proposed for the Linnean Society which will meet some weeks after the letter's date. Handwritten, dated 15 April, 1818 with further dating in Wallich's hand arrived 24 October.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich, pleased to hear that Wallich has resumed his role at the Botanic Gardens and thanking Wallich for his responses to Colebrooke's previous inquiries. He thanks Wallich also for sending seeds and that the plants that he sent are doing well at Kew. He asks if more can be sent. Wallich will be proposed for the Linnean Society after the Easter break and can also be proposed to the Geological Society. Colebrooke is keen to promote study on the geology of India and states information that he would like to collect. Colebrooke is pleased that Wallich is in contact with Mr Alexander of the Cape of Good Hope. He is also contemplating whether the "Gayal" would be suitable cattle for Cape of Good Hope and England and is looking into the possibility of shipping some heifers and steers. Handwritten, dated 18 March 1818, with Wallich's dating, arrived 28 July by Marchioness of Ely, answered 29 July by [Oriton]

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he gives advice on when to send plants as the current specimens were all dead when he retrieved them from the Custom House. He writes of jealousy among the Directors of India House if plants arrive for private persons and so therefore asks Wallich to send specimens to them but to continue to send him seeds. He adds thanks for geological specimens and for Wallich to forward letters of acknowledgement to General Hardwick and Dr Adams. He asks whether the other gentlemen might be interested in joining the Geological Society. Handwritten, dated 20 January 1820, received 9 July 1820.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he thanks Wallich for Nepal seeds and for rock specimens sent to him. He gives details of how various seeds and plants are growing in England mentioning Sir Joseph Banks and Mr Lambert. Wallich has been elected to the Linnaean and Geological Societies. Colebrooke will pay his fees if Wallich will reimburse to Colebrooke's agent. Colebrooke thanks for interesting papers that Wallich has sent including Captain Webb's account concerning the Himalayan mountains. Handwritten, dated 22 April 1819, dated in Wallich's hand, received 8 October.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he writes concerning the high cost of importing specimens. He therefore asks that they are no longer sent to him individually but to send seeds to other sources who have requested them and geological specimens direct to the Geological Society. Mr Scott, Dr Jack and Lt Gerard have all been made members of the Geological Society. Handwritten, dated 22 February 1821, received 14 July 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he describes the measures that he has taken to obtain an assistant for Wallich. He regrets the delay in Wallich receiving his publications. He remarks on geological specimens and asks Wallich to thank Capt. G. for the vocabulary of the Kunawar language and is unsure whether to deposit it in the Company's Library or that of the Royal Asiatic Society. He discusses his forestry plantations and the possibility of Wallich obtaining leave. He appends a memo concerning geological specimens. Handwritten, dated 27 July 1825, received 10 December 1825.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich to ask Wallich whether he would like the earlier volumes of the Geological Transactions to complete his set as they are available at modest terms. Colebrooke and Mr Lambert have had an interview to request an assistant for Wallich but, as yet, do not know the outcome. The specimens that Wallich sent are still undistributed and therefore Colebrooke suggests that Wallich apportions them to men of science in future. In a postscript Colebrooke mentions that Richardson is still sending publications to Wallich. Handwritten, dated 30 March 1824, received 29 September 1824.