Thirdly: Can you give me seeds of any Rubiaceae of the sub-order Cinchoneae, as Spermacoce, Diodia, Mitchella, Oldenlandia? Asa Gray says they present two forms like Primula. I am sure that this subject is well worth working out. I have just almost proved a very curious case in Linum grandiflorum which presents two forms, A and B. Pollen of A is perfectly fertile on stigma of A. But pollen of B is absolutely barren on its own stigma; you might as well put so much flour on it. It astounded me to see the stigmas of B purple with its own pollen; and then put a few grains of similar-looking pollen of A on them, and the germen immediately and always swelled; those not thus treated never swelling. Fourthly: Can you give me any very hairy Saxifraga (for their functions) [i.e. the functions of the hairs]? I send you a resume of my requests, to save you trouble. Nor would I ask for so much aid if I did not think all these points well worth trying to investigate. My dear old friend, a letter from you always does me a world of good. And, the Lord have mercy on me, what a return I make. LETTER 602. TO J.D. HOOKER. Down, October 4th [1861]. Will you have the kindness to read the enclosed, and look at the diagram. Six words will answer my question. It is not an important point, but there is to me an irresistible charm in trying to make out homologies. (602/1. In 1880 he wrote to Mr. Bentham: "It was very kind of you to write to me about the Orchideae, for it has pleased me to an extreme degree that I could have been of the least use to you about the nature of the parts."--"Life and Letters," III., page 264.) You know the membranous cup or clinandrum, in many orchids, behind the stigma and rostellum: it is formed of a membrane which unites the filament of the normal dorsal anther with the edges of the pistil. The clinandrum is largely developed in Malaxis, and is of considerable importance in retaining the pollinia, which as soon as the flower opens are quite loose. The appearance and similarity of the tissues, etc., at once gives suspicion that the lateral membranes of the clinandrum are the two other and rudimentary anthers, which in Orchis and Cephalanthera, etc., exist as mere papillae, here developed and utilised.