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[Darwin annotation: "Ask permission to quote"]

Extracts from MS of Vol. 4 of Cybele Britannica.

Perhaps the tabular & numerical form may best illustrate the wide diversities of view as to species, prevalent among botanists who have published Floras of the British Islands within the last half century or a little more. The number of species into which the several Authors have divided some of the larger genera, is indicated opposite their names in the subjoined list; changes in the genus under which any given species was placed, being allowed for in reckoning the number of species. The same sort of allowance, towards reduction of numerical discrepancies, could not be made so exactly in the case of added species; because it is occasionally very difficult to decide whether an Author was unacquainted with the "species" since described as novelties by his successors, or whether he had regarded them simply as states or varieties of those which were described by himself. I use such editions as happen to be at hand, identifying them by their dates.

		Rubus.	Salix	Hieracium.	Potamogeton	Saxifraga.	Poa.
Withering	1796	6	22	10	11	11	14
Hudson	1798	5	18	7	12	9	14
Smith	1800	7	45	10	10	14	15
Withering	1812	7	48	13	13	13	16
Smith	1818	8	56	16	12	20	17
Gray	1821	8	56	16	14	25	20
Smith	1828	14	64	16	13	25	15
Hooker	1835	13	71	18	l5	21	14
Lindley	1835	21	29	17	12	24	15
Hooker	1842	14	70	l3	17	16	15
Babington	1843	24	57	19	19	20	20
Arnott	1850	5	37	18	18	16	16
Babington	1856	41	32	33	21	20	21

16v

Thus, whether we compare together different Authors publishing at nearly the same dates, or the same Author publishing at different dates, much discrepancy appears in their ideas of species. But a separate comparison, or rather contrast, between the varying views of the same Author at short intervals, may even more convincingly prove how uncertain still are the practical ideas about species, as put forth by technical botanists whose business it should be to know species, but who too often only describe them … … … … .

Four successive editions of Babington's Manual of British Botany, to appearance each one carefully revised, have been published in about a dozen years. The Author of the Manual may be said to know the special botany of the British Islands far more completely & critically than either the first Author or recent Editor (Dr Arnott, editions 6 and 7) of the British Flora. I therefore take the four successive editions of the Manual, dated in 1843, 1847, 1851, 1856; and from these I select a score of the genera or sub-generic sections, which are differently divided into species in the several editions. (See the table on the opposite page.)

Such lists as these ought to convince any reasoning man, who may hitherto have imagined Botanic Species to be things fixed and certain in nature, that nevertheless, down to the present time, they are far indeed from being fixed and certain in books. Where then is the proof of their certainty & fixedness in nature? If in existence anywhere, in regard to the plants of England, it ought to be found in the books of a diligent Botanist, who has devoted his attention during many years specially to the plants of this one country, comparatively of small area; who has travelled much over that area, as a practical investigator; and who has well studied the descriptive works relating to the same species of plants in adjacent countries. And yet the books of this Botanist, so far from furnishing proof of fixedness, evidence great uncertainty and variability.

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Number of Species under 20 genera, by Babington's Manual, 4 editions.

	1843	1847	1851	1856
Rubus	24	36	43	41
Salix	57	58	33	31
Hieracium	19	21	27	33
Galium	15	15	14	17
Atriplex	10	11	9	9
Epilobium	10	10	11	12
Batrachium	4	5	7	12
Arctium	2	2	2	5
Ulmus	7	7	2	2
Filago	3	3	5	5
Cerastium	9	9	8	8
Lastrea	6	8	8	8
Quercus	3	3	1	1
Thlaspi	3	3	4	4
Urtica	4	4	3	3
Sparganium	3	3	4	4
Barbarea	4	3	3	3
Polystichum	2	3	3	3
Pyrethrum	3	3	3	2
Glyceria	2	3	3	3

N.B. The genera are so placed in this list as to bring into view the fact, that the changes are not in one direction only, but in the two contrary directions of in- crease and decrease of numbers; and further, that the two kinds of change occur both in large and in small genera.

[Darwin annotation: "Nothing can show more forcibly that species are not definite like sulphuric or nitric acid" The editors of the Correspondence noted: "CD alludes to James Dwight Dana's analogy between the fixity of species and that of chemical substances. Dana had presented this argument for the immutability of species in Dana 1857, which CD read in December 1857 (see Correspondence vol. 6, letter to J. D. Hooker, 25 December [1857])."]