My dear Hooker

I am become a good deal interested in crossing speculations, though I can come to no certain conclusion.— With respect to Trees, which from number of flowers on same individual offer, considerable difficulty to the probability of crossing, I want to know whether the following would cost you much trouble, & whether you feel the least interest on the point.² I have had copied in good hand a list in order, divided into Families, of the 700–800 New Zealand plants.³ Now I have no idea how far you have in your mind the memory of the N.Z plants: if distinctly it would not take you half an hour to go over the list (as many Families might be skipped) & mark with pencil cross the Trees & double Pencil cross those which were also mono- or diœcious or polygamous.⁴ I tried to do it, but broke down in not being able to decide between bushes & trees, & this must be arbitary.— I have done the few Trees of England, taking Loudon as rule what to call trees & what bushes, & you will see result.⁵ If N. Zealand with so different a Flora gave at all same result, it would appear probable that there was some connection between trees & the separation of sexes (which w^d. favour crossing).—⁶ Loudon calls the Viburnum, Box, Arbutus & Juniper Bushes.—

I think in your N. Zealand Flora you have given the number of plants of all kinds with separated sexes, which would have to be considered in the result.—

Now it will wholly depend on the state of your memory whether this would be worth doing, as it would by no means be worth your having to consult your own Flora.— What say you? Shall I send the M.S. list? Can you tell me genus of enclosed seed, which was in Birds Dung & has since germinated.—⁷

Ever yours | C. Darwin