To P. H. Gosse   7 April [1864]¹

My dear Sir

If you place large sized pollen on the stigma of any plant & 12° or 18 hours afterwards place the pistil under rather a strong power of a simple microscope & with 2 needles gently tear up the stigma you will easily see the tubes.² If the pollen be minute it is almost necessary to dissect under $\frac{1}{10}$ inch focal distance; but by gently & blindly teazing the stigma & then transferring the object to the comp. micro: you can generally see the tubes.³ If you once get to know their appearance with any pollen as with geranium, you will never mistake them in any other plant.

I have been almost confined to my bed room for 6 months & therefore cannot aid you about the exchange of Orchids but I fear you will find it difficult to exchange Catasetums,⁴ for I lately applied to Mess^rs Veitch⁵ for species & they informed me that they were so little valued that there were none in the market.

I believe some bi-generic crosses have been made but as the seeds do not germinate, it is impossible to know that the seeds are really well developed

I wish I c^d write at more length, Believe me | Sincerely yours | Ch. Darwin