Dear Oliver

Many thanks about Phyllotaxy. Your cases seem sufficient & when next in London, I shall hear what Falconer has to say.² Do not look for any more cases; but if you sh^d. stumble on them, please let me hear. I find the subject very difficult to understand; indeed I cannot understand several most simple points, such as whether there is ever more than one spire; but when Hooker comes he may be able to enlighten me.³ I must learn the elements to understand force of Falconer’s objections: he considered the laws as fixed as that of the attraction of gravity!—

I see what Treviranus says about Primula longiflora;⁴ I sh^d. like to know (if you are up in Primula) whether this species is closely allied to P. Scotica; because M^r J. Scott of Bot. Garden of Edinburgh, has been carefully observing Primulas (& I feel a conviction that he is trust-worthy) & he says P. Scotica is never dimorphic, & is much surprised, as he says it is so like P. farinosa: he has sent me plants of both, but they look very sickly.⁵

By the way I see M^r Bentham makes P. Scotica var. of P. farinosa;⁶ would it not be worth while to tell him of M^r Scotts observation;⁷ for there can be no doubt that this difference indicates an important functional difference. Unless indeed P. farinosa presents 3 sexual forms; but then they all three would grow together.

Treviranus in his Review of the Orchids⁸ does not seem to appreciate at all the prettiness of the adaptations, which seems to me the cream of the case.

Yours very sincerely | Ch. Darwin