Island floras; relationships with mainland. Ranges of species in mundane genera.
Galapagos plants one-third done.
Acot. & Moncot are done, 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
With regard to the dissimilarity between the Flora of the several Islds of the group,
that is too extraordinary a circumstance for me to offer any remarks upon, until the
florula is drawn up, the further I proceed the more I wonder. Had the
collections been all made by yourself I should have attributed it to accident, but
Macræ's collections are large from Albemarle
Isld, & the only 3 plants I have hitherto examined from (Malden Isld
(which is it?) are different from those of the other Islets— I was not aware of the analogous fact with regard to the Sandwich group; nor
have I yet examined the Canary Isld. Campbell Isld, 2 degrees further
S. than Auckland, contains several species not found
in the former, though the latter is the smallest & furthest South— I
should not think however that it would hold with Islds in the more temperate zones
generally, as the Azores which have not very many peculiar plants I shall however sift
this subject with my friend Mr H. Watson.. I have
hitherto come to no plants with seeds particularly adapted for transmission; those that
afford such facility most markedly, are the Compositæ, &
those of the Galaps are the most widely dissimilar from those of any other country of
all the Nat. Ords (as far I have seen)— It is I think high time throw
overboard laying much stress on the subject of the migration
of seeds, except in the cases of lands we know to have been recently formed,
or, from devastating causes, to be recently clothed with vegetation— From what
I have seen of the collection, I have no reason to suppose that more than one or two of
the plants are introduced, even if they were. This leads me to another Question which I
am obliged to you for directing my attention to.— “Whether the
species of large mundane genera have as wide a range as those of small
genera?”— Now the how to set about the solution of this question has
puzzled me sorely. In the first place it is not fair to compare the large genus of one
Nat. Ord. with its equivalent of small genera of another; & so, a Nat. Ord. must
be taken which has a large genus & as many species as that genus contains
scattered through a considerable number of smaller ones— Again the Nat: Ord.
must be a Mundane one, or there will not be geogr. scope for the observations. This is
not all;—Ericeæ is a large mundane Order, but its largest
genus Erica is confined to Cape & Europe, & there are none of
its species common to both, or any at all in all the New World. Lastly the Nat Ord must
be worked out pretty well. There are 3 orders which answer these conditions
well—Ranunculaceæ, Cruciferæ &
Caryophylleae, then comes another difficulty. There are degrees of
distribution. However I put the degrees aside & start with the question in its
simplest & boldest form—thus, What species are common to the old
& new World?—here two more bugbears occur, at the North where the
world gets very small the countries become in a measure identical, & which am I
to call Greenland whose Botany is Europæan? that is easily got over by
asserting—lastly a Europæan plant being found in N
W. America must not be included as a widely spread one, as the Botany of that
corner is Identical with Siberia & Kansckatha, & many plants are found
only in these two spots.. The following is then my proposition (theorem
rather)— What proportion of the Ranunculaceæ of the Old World
including Greenland & N W Am (W of the Rocky Mts) is common to the American
continent?—& secondly Do the larger proportion of these plants belong
to large genera or small.?— In answer to the latter
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, men of unerring sagacity & discrimination— The
results, if De Candolle's 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
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).— 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?..
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
It hardly appears, either that the genera are distributed equally through all the
Believe me to remain yours most truly | Jos D Hooker.
- f1 737.f1Acotyledons, 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.
- f2 737.f2J. 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.
- f3 737.f3James 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.
- f4 737.f4Hewett Cottrell Watson was botanist to the H.M.S. Styx survey of the Azores in 1842.
- f5 737.f5Torrey and Gray 1838–43.
- f6 737.f6Augustin Pyramus de Candolle, whose Prodromus systematis naturalis was an authoritative botanical text, see A. P. de Candolle and A. de Candolle 1824–73.
- f7 737.f7Both Cycadeæ and Coniferæ are very ancient groups of plants.
- f8 737.f8Paul 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.
- f9 737.f9Charles Lyell and William Henry Fitton were both on the council of the Geological Society in 1844.
- f10 737.f10CD 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].