Copy letter from Francis Alexander Towle, Assistant Secretary of the Royal Society; to P. H. H. Gray Esq.; Rothamstead Experimental Station, Harpenden, Herts. Gives P. H. H. Gray permission to reproduce the illustration from the paper by Mr [Henry Gerard] Thornton and Miss [Winifred Elsie] Brenchley originally published in the Proceedings Volume B.98, in 'Discovery'. 11 June 1927