Origin of Species Variorum

→ am forced to believe that in certain regions, as in India, 1866

do not doubt that 1859 1860 1861

→ in Europe had migrated over at least 1866

had migrated some 1859 1860 1861

→ OMIT 1866

from their native country 1859 1860

from their native country, 1861

→ from five to six 1866

six or seven 1859 1860 1861

→ OMIT 1861 1866

I suppose that 1859 1860

→ at the height of four or five thousand feet, as so 1866

as 1859 1860 1861

native

ranks

ranks,

and have reached or even crossed the equator. The invasion would, of course, have been greatly favoured by high land, and perhaps by a dry climate; for Dr. Falconer informs me that it is the damp with the heat of the tropics which is so destructive to perennial plants from a temperate climate. On the other hand, the most humid and hottest districts

will

would

have afforded an asylum

for

the

tropical

....

natives. The mountain-ranges north-west of the Himalaya, and the long line of the Cordillera, seem to have afforded two great lines of invasion: and it is a striking fact,

lately

....

communicated to me by Dr. Hooker, that all the flowering plants, about forty-six in number, common to Tierra del Fuego and to

Europe

Europe,

still exist in North America, which must have lain on the line of march. We might of course speculate on the land having been formerly higher than at present in various parts of the tropics, where temperate forms apparently have crossed; but as the lines of migration have been so numerous, such speculations would be rash.

But

Hence

I →am forced to believe that in certain regions, as in India, some temperate productions entered and crossed even the

lowlands

lowlands

of the tropics at the period when the cold was most intense,— when arctic forms →in Europe had migrated over at least twenty-five degrees of

latitude

latitude,

→OMIT and covered the land at the foot of the Pyrenees. At this period of extreme cold, I believe that the climate under the equator at the level of the sea was about the same with that now felt there at the height of →from five to six thousand feet. During this the coldest period, →OMIT large spaces of the tropical lowlands were

clothed

probably clothed

with a mingled tropical and temperate vegetation, like that now growing with strange luxuriance at the base of the Himalaya, →at the height of four or five thousand feet, as so graphically described by Hooker.