# From J. D. Hooker [23 February –  6 March 1844]

Acot. & Moncot are done,1 as also a few Dicot.— I expect to come to a rule about several groups of Islds. lying to the W. of large continents of Land in the S. Hemisphere; & hope to prove that they contain a vegetation analogous to that of those continents 20 degrees nearer the adjacent Pole. The Flora of the Galapagos is most allied to that of the S. United States & to that of S. Brazil partially,.— That of St. Helena to the Cape—Remotely it is true, but to none other:—of Tristan d’Acunha to what one would suppose the Cape to be if produced to 50 S., where the Antarctic forms would appear— Though the Galapogean Flora is essentially S. American, the proportions of the Nat: Ords to one another is remarkably different, as is the vast quantity of Arborescent Compos. & particularly of Euphorbiaceæ (at which I am now working) & which order has no less than 19 representatives, 16 of them entirely new, they are however of very common genera, Euphorbia, Acalypha Croton & Phyllanthus. Now it is very remarkable, that in an order so poorly represented as Graminæa (& where genera are so mundane), there should be a new genus, & no less than 6 old ones,.—7 genera for 11 species; while in Euphorbiaceæ there are only 4 genera for 19 species—I think in the paucity of grasses there will be a strong analogy to other Tropical Islds;—2 the reverse holds good in the Islands of higher Latitudes. I wish that the Admiralty had returned me my notes that I could draw out some proportions to send you—

These results may I think be relied on as far as they go, but they would not have been attainable had we not the N. American flora of Torrey & Gray,5 men of unerring sagacity & discrimination— The results, if De Candolle’s6 work alone had been taken, would be erroneous; because he makes species of N. Am plants since discovered to be forms of Europæan, & because the species of the genus have increased in a greater ration than small genera have, & plants common to the two have not turned up in the same proportion— Again De. C had not the means of knowing whether some of those common were introduced into the New World or not—Torrey & Gray carefully discriminate these—

What a remarkable fact you mention that the Geog. distrib. of shells is proportional to their persistence in nature. This is a wrinkle to Botanists towards the detection of the orders of fossil plants.. But Cycadeæ are certainly not widely distributed. Pines are (Coniferæ I mean).—7 Do you know any thing of a Mr (Count) Streletski who I hear is in Town & of whom we saw a good deal in V. D. Land?.. 8

I have a list of the principle peat earth plants with an attempt at arranging them according to the proportion each yields: I include more plants than you mention, but your Journal is not before me as I lent it a few days ago— Enclosed is a list of as far as I have gone with the Galapago Isld plants, whenever you return it I will add to it & send it again—I think I have about $\frac{1}{3}$ done, the proportion of new sp. is terrible among Dicot. & I must perpetrate one or two genera.

It hardly appears, either that the genera are distributed equally through all the Islds.,—or that seperate Islds have seperate genera; untill however I have gone through the collection I shall forbear any more remarks, as I am often woefully out when applying the numerical test to my preconceived Ideas— I hope to be at the Geological Soc. this next weeks meeting as I have not seen Mr Lyell or Dr Fitton yet,9 & my Father will go if the weather is tolerable.— I think this letter will tire you out, I wish I could be as useful to you as you are to me in suggesting these most interesting questions from which when properly worked out we may begin to ascend to grand causes

Believe me to remain yours most truly | Jos D Hooker.

## CD annotations

1.11 Euphorbiaceæ… Tropical Islds;— 1.18] scored pencil; ‘Large Genera’ added in pencil over scoring
2.6 Malden … from] scored pencil
scored pencil
2.9 Auckland, contains] ‘[reverse question mark].representative species’ added pencil
2.22 “Whether… small genera?”— 2.23] scored pencil
‘Hence Species of small genera have narrower ranges than the species of large mundane genera’ added ink
4.1 shells] del pencil; ‘not forms’10 added pencil
scored pencil
crossed pencil

## Footnotes

Acotyledons, one of Antoine Laurent de Jussieu’s three major plant divisions, equivalent to Linnaeus’ Cryptogamia, i.e., fungi, algae, mosses, and ferns. At this time, Hooker included gymnosperms (cycads and conifers) in his definition of monocotyledons.
J. D. Hooker 1846, p. 242, states that the number of grasses on the Galápagos is much less than on other tropical islands, like the Sandwich and Cape Verde groups.
James Macrae collected plants on the Sandwich and Galápagos Islands for the Horticultural Society of London. He travelled with George Anson Byron in H.M.S. Blonde.
Hewett Cottrell Watson was botanist to the H.M.S. Styx survey of the Azores in 1842.
Torrey and Gray 1838–43.
Augustin Pyramus de Candolle, whose Prodromus systematis naturalis was an authoritative botanical text, see A. P. de Candolle and A. de Candolle 1824–73.
Both Cycadeæ and Coniferæ are very ancient groups of plants.
Paul Edmund de Strzelecki, who had explored parts of the Australian interior and Tasmania (Van Diemen’s Land) in 1839–40. He returned to Britain in 1843.
Charles Lyell and William Henry Fitton were both on the council of the Geological Society in 1844.
CD sometimes used ‘form’ to mean genera or higher groups. He is objecting to Hooker’s extending his query on ranges of species to ranges of orders. See letter to J. D. Hooker   [6 March 1844].

## Summary

Island floras; relationships with mainland. Ranges of species in mundane genera.

Galapagos plants one-third done.

## Letter details

Letter no.
DCP-LETT-737
From
Joseph Dalton Hooker
To
Charles Robert Darwin
Sent from
unstated
Source of text
DAR 100: 10–11
Physical description