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Darwin Correspondence Project

From Berry Benson   9 February 1870

Augusta, Ga.

Feb. 9th. 1870.

Mr. Charles Darwin.

Dear Sir:

I have read your work on “The Origin of Species” with a great deal of interest, and beg to express my gratitude in a simple way for opening to me the gate to such broad fields of knowledge and thought, hitherto so basely explored.

In your chapter on “Geographical Distribution” (XI.) on the subject, “Means of Dispersal”, (Page 318 of the edition published by D. Appleton & Co. N.Y.) is the following:1

“It would be a great error to argue that because a well-stocked island like Gt. Britain, has not, as far is known (and it would be very difficult to prove this,) received within the last few centuries, through occasional means of transport, immigrants from Europe, or any other Continent, that a poorly stocked island, though standing more remote from the mainland, would not receive colonists by similar means.”

To put in your hands proof, (if true,) that your island has received one colonist in quite recent times, I have taken the trouble to copy the accompanying account of a waterplant, from Wells’ Annual of Scientific Discovery for 1854.2 which I remembered to have read, when I came across the passage in your book above quoted.

If you have ere this had your attention called to the same, or if it may not prove useful to you, as I had been led to hope, pray excuse my having so far intruded on your valuable time. But if the account does have a direct bearing on the point in question, and proves serviceable to you, please accept it as the partial expression of the obligation due you, for the pleasure & satisfaction derived from studying your inestimable work.

Very Truly Yours. | Berry Benson.


Extract from Wells’ Annual of Scientific Discovery. 1854. Page 334. Trübner & Co, London. “Curious Fresh Water Plant.

A recent number of the Edinburgh Journal contains a description of a new and singular fresh-water plant, which has recently appeared in the inland waters of Gt. Britain, filling her canals, lakes and streams, and threatening, unless a remedy be speedily discovered, to interfere seriously with, perhaps to destroy, all or most of her facilities for inland navigation and drainage.3 This terrible foe is a species of aquatic weed, the first specimen of which was discovered in the year 1842, in the lake of Dunse Castle, Berwickshire, Scotland. The appearance of the little vegetable stranger excited considerable interest among botanists, and the discovery was duly noted in various scientific publications; speciments were sent to a few individuals, and then—it was forgotten. But the plant was of too aspiring a character to live and blush unseen in British waters. In 1847, it was found growing in great abundance, and closely matted together, in the reservoir adjoining the Foxton Locks, on the Canal in Leicestershire. This discovery induced a re-examination of the original plant, when it was found that the long-neglected water-weed had travelled out of the lake, and was making its way down the Whiteadder to join the Tweed. In the same season it was found in great profusion in a tributary of the Trent, in Nottinghamshire, and it was also discovered to exist in “dense masses, and great abundance” in the Watford Locks, Northamptonshire. In 1849, it appeared in Derbyshire and Staffordshire, “forming very large submerged masses, of a striking appearance,” in the Trent and adjoining canals. In 1850, it was found near Rugby, in Warwickshire; and in 1851, it was discovered in the rivers Ouse and Cam, near Cambridge.

The botanical interest which was at first excited by the discovery of large quantities of this new plant in various districts, at nearly the same time, soon gave place to a feeling of serious alarm prompted by the injurious effects of its unparalleled increase. A year after it was first noticed in the Cam, the stream near the Colleges was so blocked that extra horses were required to draw barges through the vegetable mass. A year after its appearance at Ely, the railway dock became so choked with the weed that boats could not enter until several tons of it had been removed. In many places fishermen were obliged to discontinue setting long lines, or using nets, because the weed either carried them away or stripped them of the fish. It is evident that this plant, styled by Mr. Babington, of Cambridge, the anacharis alsinastrum, cannot a great while have been a native of Gt. Britain.4

If so, its remarkable prolific powers would long since have brought it into notice. And it is a noteworthy fact that the anacharis is dioecious,—that is, the male and female flowers grow on separate individuals,—and all the plants known to exist in England are females. This fact affords an almost positive proof that only one stem or seed of a female plant was the progenitor of all the anacharis in Gt. Britain; and this seed was possibly introduced from Canada in the crevice of some one of the many logs which are annually conveyed across the ocean to England, and of which so many have been used in the great rail-road works at or about Rugby. It is thought that in the clear, swift-flowing rivers of America, the weed would not form the immense masses which characterise its growth in the sluggish and—as they contain a greater amount of inorganic animal and vegetable matter,—more nourishing waters of the English rivers and canals. But our readers will inquire how—as only the female anacharis has been discovered in England, and it is therefore unable to propagate seed in that country,—how it contrives to extend itself so rapidly and widely, and wherein are its prolific powers vested. These questions are easily answered; its leaves, which grow in threes, around a slender stem, are studded with minute teeth which cause them to cling to every object with which they come in contact, and the stem is so very brittle that whenever the plant is disturbed pieces are broken off; and as every fragment of the stem is capable of becoming an independent plant, producing roots and leaves, and extending itself indefinitely in every direction, it is evident that the anacharis must be in an almost continual state of reproduction. All the localities in which this singular plant seemed to appear almost simultaneously, are reducible to two,—Dunse Lake, in Berwickshire; and the Foxton Locks, in Leicestershire. It probably originated in the Foxton Locks, and was afterward introduced into the former place. The Foxton Locks are in direct communication with nearly all the English localities of the plant, and a single sprig of the anacharis would in a very short time inoculate any connected water-system, from one end to the other. The plant was introduced by scientific men into the Cam, and other places, originally for experimental purposes, and is of such a nature that, clinging to the bottoms of vessels or boats, it might easily inoculate other streams and waters.

In the case of the Cam, in the short space of four years, it multiplied so, from a single stem, as to impede both navigation and drainage. It has become a great and growing evil; and the attention of scientific men— of practical men— is loudly demanded to the subject of its extinction.”


Benson refers to Origin US ed.: in the first English edition, the pages referred to are 364–5.
The Annual of Scientific Discovery; or Year-Book of Facts in Science and Art was published in Boston, Mass., and was edited by David Ames Wells and others.
The reference is to Chambers’s Edinburgh Journal n.s. 19 (1853): 372–3.
Anacharis alsinastrum is now Elodea canadensis. For CD’s interest in the plant, see Correspondence vol. 5, Correspondence vol. 7, letter to J. D. Hooker, 31 December [1858], and Correspondence vol. 8, letter to J. S. Henslow, 2 April [1860] and nn. 2 and 3, and letter to William Marshall, 9 April [1860]. Benson also refers to Charles Cardale Babington.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Origin US ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. A new edition, revised and augmented by the author. By Charles Darwin. New York: D. Appleton. 1860.


Compliments Origin.

Sends extract about a waterplant to illustrate CD’s points about the means of dispersal in geographical distribution.

Letter details

Letter no.
Berry Benson
Charles Robert Darwin
Sent from
Augusta, Ga.
Source of text
DAR 160: 148
Physical description
2pp, encl 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 7099,” accessed on 10 December 2019,

Also published in The Correspondence of Charles Darwin, vol. 18