[E26]

March 23d. 1861. Suppose world shortly before Glacial to have had present temperature; but we know before that it was hotter. Probably the effect of this then would have been an Equatorial Flora, which could live only in hottest regions; & in N. Tropical & S. Tropical Flora fitted for less intense Heat, & distinct from each other, for they must have been separated from each other for long time by Equatorial Flora. During Glacial period, I suppose Equatorial Flora almost wholly annihilated, and to N. & S. Tropical flora, which would both have suffered quite so much under Equator during Glacial period, to have occupied Equatorial regions. Their commingling would have made a rich flora, & which now has become accustomed to rather hotter climate than that to which they were accustomed, previously to Glacial period.—

[diagram]

35° North

N. Tropical Flora

20° N.

Equator

Equatorial Flora nearly all exterminated during Glacial period.

20° S.

S. Tropical Flora distinct from north

35° S.

over

 

[E26v]

All this upset by Mr Bates paper.—

Can species have been very largely developed since glacial period.—

Certainly from Lat 25° to Equator productions here ought to have very uniform character.

How is this?

In Brazil S. America immigration must have been almost exclusively by lines of mountains —

 

Crowning difficulty is why equatorial production not all destroyed as climate some of temperate must have been best fitted for sub-tropics productions — Probably was & our first Temperate productions were sub-tropical before glacial.— All Fauna & Flora most disturbed & a few temperate forms crossed owing to disturbance— taking advantage of high land—

With respect to S America we have but little evidence

Region of [words illeg] seen
is greatest difficulty — Undoubtedly there is much to explain as yet