A series of four long Autograph Letters Signed, to Mr. Elwes, about the principles of experimental fruit farming, horticultural theories, observations of plant growth, and much else. 4 letters. 9 pp. 10 x 8 inches, minor blemishes only. With an offprint of his article, The Effect Of One Plant on Another (1917). Woburn Experimental Fruit Farm, 1917. Percival Spencer Umfreville Pickering (1858-1920), chemist. From 1894 on, he was director of the Woburn Experimental Fruit Farm, a private establishment by Pickering and the Duke of Bedford, where he worked to improve horticultural techniques.