Darwin included a brief citation of “Mr. Patrick Matthews” (misspelt) in Chapter 21 of Variation of Animals and Plants under Domestication (1868). This book was intended as the first instalment of his three-part magnum opus expanding on the “abstract” given in On the Origin of Species, but the other instalments were never completed.
Matthew is cited in reference to the idea that domesticated species that have not been under intense selection display greater and more continuous variety than either wild or highly domesticated species, because they are free from the constraints of either natural or artificial selection:
Analogous facts have been observed with plants: the nutmeg-tree in the Malay archipelago is highly variable, but there has been no selection, and there are no distinct races.48 The common mignonette (Reseda odorata), from bearing inconspicuous flowers, valued solely for their fragrance, “remains in the same unimproved condition as when first introduced.”49 Our common forest-trees are very variable, as may be seen in every extensive nursery-ground; but as they are not valued like fruit-trees, and as they seed late in life, no selection has been applied to them; consequently, as Mr. Patrick Matthews remarks,50 they have not yielded distinct races, leafing at different periods, growing to different sizes, and producing timber fit for different purposes. We have gained only some fanciful and semi-monstrous varieties, which no doubt appeared suddenly as we now see them.
The citation (Footnote 50) is to a part of Excerpt 3: “50 ‘On Naval Timber,’ 1831, p. 107.”
Apart from the spelling mistake in Matthew’s name, the citation above also displays an apparent lack of thematic care on Darwin’s part. On the page cited, Matthew is actually arguing an altogether different case for nursery-raised forest trees than the one attributed to him by Darwin. Darwin’s claim is that Matthew argues for a lack of distinct races, and greater continuous variation, in these trees. He also implies that Matthew argues that these trees are subject to no selection. In fact, neither of these arguments is put forward by Matthew. Matthew argues that there is selection going on in these trees, but of a counter-productive sort that is leading to deterioration of tree vitality. He writes: “the small growing and weakly varieties … have been continually selected as reproductive stock”. He makes no statement regarding the distinctness of forest tree races, nor of the extent of variation in leafing time, size attained or timber produced. Instead, he makes this statement with regards to more domesticated species, not forest trees (from Excerpt 3): “…in the Apple, Pear, Plum, Gooseberry, Potato, Pea, which sport in infinite varieties, differing considerably in size, colour, taste, firmness of texture, period of growth, almost in every recognisable quality”.
Eiseley (1959, pp.109-111), repeated in Eiseley (1979, pp.71-3), has argued that there is more going on here than an apparent lack of care on Darwin’s part. He points out Darwin makes more or less the same statement about “forest trees raised in nurseries” in his unpublished 1844 essay on natural selection, but this time without citing Matthew: “In the case of forest trees raised in nurseries, which vary more than the same trees do in their aboriginal forests, the cause would seem to lie in their not having to struggle against other trees and weeds, which in their natural state doubtless would limit the conditions of their existence”. Eiseley then notes that a different page in Matthew, book – p.308 from Excerpt 4 – has a sentence more in line with Darwin’s statement in his 1844 essay, although once again it doesn’t match up entirely because Darwin is arguing that the less domesticated species under Man’s care are more continuously variable, while Matthew is again saying (as he does in Excerpt 3) that the more domesticated species (for example, orchard trees rather than forest trees) display a greater range of discrete varieties: “Man’s interference, by preventing this natural process of selection among plants, independent of the wider range of circumstances to which he introduces them, has increased the difference in varieties, particularly in the more domesticated kinds”. Eiseley notes that Matthew’s phrase “natural process of selection” in the latter quote may have been the inspiration for Darwin’s use of “natural means of selection” in his 1842 and 1844 unpublished essays, and thence “natural selection”. Finally, he notes that Darwin writes in a Letter to Asa Gray of 20 July 1856 that “all my notions about how species change are derived from long continued study of the works of (and converse with) agriculturists and horticulturists”.
In fact, there’s an even better (i.e. more contemporaneous) version of Darwin’s latter quote in his Letter to J. D. Hooker of 11 Jan 1844, where the famous “confessing a murder” quote also lies: “Besides a general interest about the Southern lands, I have been now ever since my return engaged in a very presumptuous work & which I know no one individual who would not say a very foolish one.— I was so struck with distribution of Galapagos organisms &c &c & with the character of the American fossil mammifers, &c &c that I determined to collect blindly every sort of fact, which could bear any way on what are species.— I have read heaps of agricultural & horticultural books, & have never ceased collecting facts—At last gleams of light have come, & I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.”
Eiseley takes all this as evidence that Darwin had read Matthew’s book before 1844. Sutton (2014 and 2015) has proposed an alternative scenario, that Darwin may have read the works of David Low or Robert Mudie, who in turn may have been influenced by Matthew. Alternatively, the blogger Joachim D has proposed that both Matthew and Darwin may have independently obtained this idea from earlier writers who wrote some similar ideas on variation under domestication, including Buffon (1764), Knight (1801), and Loudon (1806 and 1822). The case remains open, as all the evidence is circumstantial.