To Charles Lyell 14 June 1831

Dear Lyell,

With the exception of a few verbal corrections, I have only one other alteration to suggest, at p 55. Your allusion to the mode of impregnation is not sufficiently accurate. It is not the pollen which is imbibed but the fovilla or rather minute granules which each globule of pollen contains. The process is most curious & is fully detailed in a paper of A. Brogniart's in the 4th (?) vol. of the Ann. des Sciences - (I have it separate if you wish to see it. When ripe pollen is placed in water it explodes & the granules are dispersed, but when the pollen adheres to the glutenous exudations in the Stigma, no effect of the sort takes place. It remains there for hours unchanged until the flower begins to fade. There may be seen one, two, or more delicate membranous tubes exuding thro' certain pores or valves in the pollen-grain. These insinuate themselves between the utricles of the stigmatic tissue - & Brog^t says the granules are emitted thro' their extremity. Brown doubts this - & Amici (very lately) declares that these granules bag & all descend down the whole length of the style to the ovule [Drawing of 'pollen emitting its bags, utricles of stigma']. The bags appear to be an internal lining forced thro' the external by contractions, according to Brog^t they are certainly to be detected. I have seen them repeatedly - & Brogniart's observations have been verified by several. It is easy to imagine that were several difft kinds of pollen placed on the stigma, that kind only w^d be acted upon w^h was most congenial to the habits of the plant - tho' if one kind only were allowed to be in contact with it, then an action might be induced tho' it were not of the same species with the plant. Brog^t suggests a limit to hybridity in the relative size of the granules in the pollen some not being adapted to penetrate the ovula of other species. But this is mere hypothesis & at variance with Brown's notions altogether. I shall have Lowe's Madeira paper for you in a day or two & will send it with the Amici. I mistook the day for returning Books to the library. It is the 23^d not the 20^th.

Believe me

Very sincerely yrs

J. S. Henslow