[E38]

When speaking of temperate plants penetrating tropics - allude to acclimatisation during passage. Test by what plants can stand Calcutta (a most severe test: Hooker says) Dicots on S. range being due to other species. It wd be in some degrees like spread of N. plants over bare ground. Then allude to Hookers excellent remarks of far more warmer temperate than sub-arctic plants ought to have crossed Tropical. This, I presume, wd be fatal without modification doctrine; but with modification

 

[E38v]

(2

(ie according to my principles) these must have crossed Equator long before sub-arctic & therefore have been exposed to more change. (just like species of alpine compared to N. lands & islands). Therefore I shd expect that there would be in S. far more representative species, (but fewer identical) to temperate forms, than of sub-arctic.

N.B. I shd put that many of the temperate & sub-arctic forms which penetrated to Tropics wd. retreat again N. other wd remain on higher land other cross to the South