The explanation of the sterility of the seed-capsules of the Cypripedium sent to me I have little doubt lies in the circumstance of their having been fertilised by pollen taken from the same plant or seedling.² I now know of a long series of cases in which various orchids are absolutely sterile when fertilised by their own pollen, (proved however to be as itself effective) but which can be easily fertilised by pollen taken from other individuals of the same species, or from other and quite distinct species.—³ These facts strike me as most remarkable under a Phy. point of view; & all point to the necessity with plants of regular or occasional [union] between distinct individuals of the same species.—

If these remarks are of the least value to you, with respect to the communication you can of course use them⁴

[Many thanks] for note.— I received Report & I forward to Hildebrand copy of his paper.—⁵

I am at present so busy that I have no time to carefully examine the interesting specimen which you have kindly sent me & which I return. From the remarkable fact, lately ascertained by D^r. H. that with many orchids the ovules do not become developed until many weeks or even months after the pollen-tubes have penetrated the stigma, it is not a little difficult to ascertain whether an orchid [four words illegible] [whether] the abortion of the female organs has started.⁶ Of course there is no difficulty in ascertaining the rudimentary condition of the pollen.