Dear Darwin

I was about to write today, when your jolly letter came this morning¹ to tell you that after carefully going over the N. Z. Flora, I find that there are only about 30 reputed indigenous Dicot annuals, of which almost half, not being found by Banks & Solander, are probably non-indigenous.² This is just $\frac{1}{20}$ of the Dicots. or excluding the doubtful about $\frac{1}{40}$ ^th. whereas the British proportion of annuals is ^1/4–6 amongst Dicots.!!! Of the Naturalized New Zealand plants, one-half are annual!³

I suppose there can be no doubt but that a deciduous leaved vegetation affords more conditions for vegetable life than an evergreen one—& that it is hence that we find countries characterized by uniform climates to be poor in species & these to be evergreen— I can now work this point out for New Zealand & Britain.

Japan may be an exception   It is an Extraordinary Evergreen country & has many species apparently, but it has so much novelty that it may not be so rich in species really as it hence looks, & I do believe it is very poor. It has very few annuals.

Then again I think that the number of plants with irregular flowers, & especially such as require insect agency, diminishes much with Evergreenity

Hence in all humid temperate regions we have as a rule Few species,—many evergreens, few annuals,—few Leguminosæ & Orchids,—few Lepidoptera & other flying Insects—many Coniferæ, Amentacea,⁴ Gramineæ Cyperaceæ & other wind fertilized trees & plants &c.

Orchids & Leguminosæ are scarce in Islets because the necessary fertilizing insects have not migrated with the plants. Perhaps you have published this⁵

Ever | J. D Hooker.