g archipelagoes. Here is a wriggle:
the older a form is, the better the chance will be of its having become
developed into a tree! An island from being surrounded by the sea will
prevent free immigration and competition, hence a greater number of
ancient forms will survive on an island than on the nearest continent
whence the island was stocked; and I have always looked at Clethra
(365/2. Clethra is an American shrubby genus of Ericaceae, found nowhere
nearer to Madeira than North America. Of this plant and of Persea, Sir
Charles Lyell ("Principles," 1872, Volume II., page 422) says: "Regarded
as relics of a Miocene flora, they are just such forms as we should
naturally expect to have come from the adjoining Miocene continent." See
also "Origin of Species," Edition VI., page 83, where a similar view is
quoted from Heer.) and the other extra-European forms as remnants of
the Tertiary flora which formerly inhabited Europe. This preservation of
ancient forms in islands appears to me like the preservation of ganoid
fishes in our present freshwaters. You speak of no northern plants on
mountains south of the Pyrenees: does my memory quite deceive me that
Boissier published a long list from the mountains in Southern Spain? I
have not seen Wollaston's, "Catalogue," (365/4. Probably the "Catalogue
of the Coleopterous Insects of the Canaries in the British Museum,"
1864.) but must buy it, if it gives the facts about rare plants which
you mention.

And now I have given more than enough of my notions, which I well know
will be in flat contradiction with all yours.

Wollaston, in his "Insecta Maderensia" (365/5. "Insecta Maderensia,"
London, 1854.), 4to, page 12, and in his "Variation of Species," pages
82-7, gives the case of apterous insects, but I remember I worked out
some additional details.

I think he gives in these same works the proportion of European insects.

LETTER 366. TO J.D. HOOKER.

(366/1. Sir Joseph had asked (July 31st, 1866): "Is there an evidence
that the south of England and of Ireland were not submerged during the
Glacial epoch, when the W. and N. of England were islands in a glacial
sea? And supposing they were above water, could the present Atlantic
and N.W. of France floras we now find there have been there during the
Glacial epoch?--Yet this is what Forbes demands, page 346. At page 347
he sees this objection, and wriggles out of his difficulty by putting
the date of the Channel 'towards the close o