Describes problems of classifying species in highly variable genera. Lists highly variable genera. Comments on the list of Asa Gray. Says species may be made to appear more or less variable according to whether a genus is divided into few or many species.

Urges AG to generalise from his observations on the flora of the northern U. S.

Expected to find separation of sexes in trees because he believes all living beings require an occasional cross, and none is perpetually self-fertilising. The multitude of flowers of a tree would be an obstacle to cross-fertilisation unless the sexes tended to be separate.

The Leguminosae are CD’s greatest opposers; he cannot find that garden varieties ever cross. Could AG inquire of intelligent nurserymen on the subject?

Thanks AG for information on protean genera; much wants to know whether their great variability is due to their conditions of existence or is innate in them at all times and places.

JDH thanks Asa Gray for his note of 10 Mar [1857]. Is impatient for LESSONS, apologises for not reviewing the MANUAL in the JOURNAL OF BOTANY. William Jackson Hooker wants JDH to review [Miles Joseph] Berkeley's INTRODUCTION TO CRYPTOGAMIC BOTANY, JDH praises its content but calls it 'appallingly written & arranged', a common failing of parson-authors such as Sedgwick & Buckland, Copewell[?] & Baden-Powell. An abstract of the Linnean Society's ideas on genera will appear in the LITERARY GAZETTE & a summary by Bentham in the Linnean journal. JDH is critical of the way Germans approach a subject, A. Braun's work on genera is an exemplar. JDH dismisses [Berthold Carl] Seemann's 'twaddle' about genera being objective or subjective, gives Rosa & Salix as examples of the former & Unbellifers as the 'confoundedly bad' latter. Discusses [Thomas] Thomson's paper on germination & embryos of Careya & Barringtonia. JDH worries about Gray doing a book on forest trees. Notes [Richard] Spruce is stranded in Tarapoto, in the Andes, en route to Lima. Mentions UK government expedition to the source of the Missouri & the East Rocky Mountains, [Eugène] Bourgeau is the botanist & the commander Mr Palliser. JDH's children & wife [Frances Hooker] are in Brighton. JDH suggests a visit to the UK would stimulate Gray's work on the Flora of North America. [Walter Hood] Fitch has produced plates of British natural orders, designed by [John Stevens] Henslow, for the National Schools under the Board of Trade. In a post script dated 30 Mar JDH gives a detailed opinion of Gray's ELEMENTS. JDH cannot visit Canada & USA until 1858, he has too much work, with the Indian Herbarium & Tasmanian flora for the Van Diemen's Land government, & not enough money. Comments briefly on Gray's notices in SILLIMAN & at length on De Candolle's botanical geography, referring to the work of de Heer, Henfrey, Brown, Forbe's Atlantis theory & Duchastre's encyclopaedia. Recommends that Gray get the GARDENERS' CHRONICLE.