Sends article on temporary color-blindness. G. B. Airy's book on sound [On Sound and Atmospheric Vibrations] is finished.

Observations on various forms of [hemianopsia], which afflicts HA, his father [G. B. Airy], and JH. Detailed description of recent attack. Seven sketches with captions.

JH's approval encourages HA to publish account [of hemianopsia]. JH may keep HA's drawings. Notes on attack suffered by JH.

Writing about [hemianopsia] for doctor's thesis at Cambridge. Asks permission to quote report of JH's attack [see JH's 1868-5-4].

Received JH's permission to quote JH [in HA's thesis on hemianopsia] and describe JH's latest attack, including 'patches of coloured checquer work.'

Describes difficulties in producing glass pen and attaching it to pendulum to produce precise curves for aligning equatorial [telescope mount]. Sent artistic sample to JH's wife.

Comments on discussion of residual organs in Descent [ch. 1].

Describes his ability to contract the platysma myoides at will.

Suggests reason for loss of voluntary movement of ears in men and monkeys.

Reply to CD’s letter of 5 Apr 1871 [7659], in which he asked HA for further details on when and how platysma myoides contracts.

Replies to CD’s questions about sources on leaf arrangement.

Gives news of speech and paper about CD.

Thanks for letter and reference to Nägeli’s observations on leaf arrangement in the bud.

A review and criticism of Chauncey Wright’s paper on phyllotaxy [Mem. Am. Acad. Arts & Sci. n.s. 9 (1867–73): 379–415]. Does not believe that the "distributive" and "cyclical" properties, which CW claims characterise the existing spiral orders of leaf arrangement, can be shown to be advantageous to plants. CW’s speculations on the origins of the spiral arrangement of leaves are purely hypothetical.

On leaf arrangement. [Badly damaged and almost illegible.]

Outlines his theory on the origin of existing orders of leaf arrangement. Believes spiral and whorled orders have evolved from a primitive distichous arrangement. These arrangements permit a compact bud form of small surface area that can withstand external changes in temperature, and in particular can tolerate frost.

Thanks CD for reading his MS [8412] and for his suggestions.

Clarifies his statement on the contraction of the bud-axis: did not mean to imply that this contraction occurred in an individual’s life-time, rather that it was the effect, after the course of ages, of successive favourable modifications.

Believes the true theory of phyllotaxy will give a convincing illustration and proof of the theory of evolution.

Discusses the significance of the node. Believes, with CD, that it has no independent importance but is merely the consequence of the presence of a leaf. Does not believe a distinction can be made between whorled and alternate leaf arrangements on the basis of the number of leaves springing from a node. The node, as the starting point of a leaf, is subject to any disarrangement which takes place among the leaves.

Corrects a factual error in his previous letter [8418].

Sends specimens illustrative of the "nodal" question.

Responds to CD’s comments on his MS on phyllotaxy.

The initial variation required by his theory would be a slight twist of the bud-axis; believes the frequent twisting of stems and branches renders such a variation possible.

Admits he placed too much emphasis on the importance of frost. He should have spoken more generally of "vicissitudes of climate".

Disputes Thomas Meehan’s observations on the hardiness of exposed buds, and believes bud-scales are for the protection of the bud-leaves. Reiterates his opinion that the phyllotaxy of a plant is determined by causes acting when the leaves are crowded into close contact. Attempts to explain how a different phyllotaxy on the upper and lower parts of the same shoot could have arisen.

Thanks for letter, in which CD cited [Anton] Kerner’s alpine observations.

Describes with diagrams the curious disposition of leaves on some Acacia twigs, and points out that his theory should account for these anomalies as well as normal cases.

Discusses works lent him by CD: Candolle, Kerner, Braun, Sachs, and CD’s own notes on relative positions of leaves. Plans paper on subject for Royal Society.

Just appointed medical inspector under local government board.

HA’s paper on leaf arrangement is almost ready; asks CD to communicate it to the Royal Society. Seeks permission to quote from CD’s notes.