Firstly, the red cowslip, losing its dimorphic structure and changing so extraordinarily in its great production of seed with its own pollen, especially being nearly sterile when fertilised by, or fertilising, the common cowslip. The analogous facts with red and white primrose. Secondly, the utter dissimilarity of action of the pollen of long- and short-styled form of one species in crossing with a distinct species. And many other points. Will you suggest to Oliver to review this paper? if he does so, and if it would be of any service to him, I would (as I have attended so much to these subjects) just indicate, with pages, leading and new points. I could send him, if he wishes, a separate and spare copy marked with pencil. LETTER 653. TO ASA GRAY. September 13th [1864]. (653/1. In September, 1864, Darwin wrote to Asa Gray describing Scott's work on the Primulaceae as:--) A paper which has interested me greatly by a gardener, John Scott; it seems to me a most remarkable production, though written rather obscurely in parts, but worth the labour of studying. I have just bethought me that for the chance of your noticing it in the "Journal," I will point out the new and very remarkable facts. I have paid the poor fellow's passage out to India, where I hope he will succeed, as he is a most laborious and able man, with the manners almost of a gentleman. (653/2. The following is an abstract of the paper which was enclosed in the letter to Asa Gray.) Pages 106-8. Red cowslip by variation has become non-dimorphic, and with this change of structure has become much more productive of seed than even the heteromorphic union of the common cowslip. Pages 91-2, similar case with Auricula; on the other hand a non-dimorphic variety of P. farinosa (page 115) is less fertile. These changes, or variations, in the generative system seem to me very remarkable. But far more remarkable is the fact that the red cowslip (pages 106-8) is very sterile when fertilising, or fertilised by the common cowslip. Here we have a new "physiological species." Analogous facts given (page 98) on the crossing of red and white primroses with common primroses. It is very curious that the two forms of the same species (pages 93, 94, 95, and 117) hybridise with extremely different degrees of facility with distinct species. He shows (page 94) that sometimes a cross with a quite distinct species yields more seed than a homomorphic union with own pollen. He shows (page 111) that of the two homomorphic unions possible with each dimorphic species the short-styled (as I stated) is the most sterile, and that my explanation is probably true. There is a good summary to the paper. LETTER 654. TO J.D. HOOKER. (654/1. The following letters to Hooker, April 1st, April 5th and May 22nd, refer to Darwin's scheme of employing Scott as an assistant at Down, and to Scott's appointment to the Botanic Garden at Calcutta.) Down, April 1st, 1864.