It seems to me a most curious case of distribution; and how very well you argue, and put the case from analogy on the high probability of single centres of creation.

That great man Agassiz, when he comes to reason, seems to me as great in taking a wrong view as he is great in observing and classifying.

One of the points which has struck me as most remarkable and inexplicable in your memoir is the number of monotypic (or nearly so) genera amongst the representative forms of Japan and N.America.And how very singular the preponderance of identical and representative species in Eastern, compared with Western, America.

I have no good map showing how wide the moderately low country is on the west side of the Rocky Mountains; nor, of course, do I know whether the whole of the low western territory has been botanised; but it has occurred to me, looking at such maps as I have, that the eastern area must be larger than the western, which would account to a certain small extent for preponderance on eastern side of the representative species.
Is there any truth in this suspicion?
Your memoir sets me marvelling and reflecting.

I confess I am not able quite to understand your Geology at pages 447, 448; but you would probably not care to hear my difficulties, and therefore I will not trouble you with them.
I was so grieved to get a letter from Dana at Florence, giving me a very poor (though improved) account of his health.
LETTER 350.