As you have probably a list of the introduced plants, would it be asking too great a favour to send me, per Hooker or otherwise, just the total number of genera and orders to which the introduced plants belong.

I am much interested in this, and have found De Candolle's remarks on this subject very instructive.
Nothing has surprised me more than the greater generic and specific affinity with East Asia than with West America.

Can you tell me (and I will promise to inflict no other question) whether climate explains this greater affinity?
or is it one of the many utterly inexplicable problems in botanical geography?
Is East Asia nearly as well known as West America?
so that does the state of knowledge allow a pretty fair comparison?
I presume it would be impossible, but I think it would make in one point your tables of generic ranges more clear (admirably clear as they seem to me) if you could show, even roughly, what proportion of the genera in common to Europe (i.e.nearly half) are very general or mundane rangers.

As your results now stand, at the first glance the affinity seems so very strong to Europe, owing, as I presume, to nearly half of the genera including very many genera common to the world or large portions of it.

Europe is thus unfairly exalted.