1. The amide, tyrosine, tryptophan, cyst(e)ine, methionine, arginine, histidine and lysine contents of protein preparations from senescent leaves of Trifolium 8ubterraneum, expressed as percentages of the protein N occurring in these for'ms, were found to be 5-39-5-71, 2-80-2-90, 1-65-1-85 (best 1-80), 1-42-1-47, 1-02-1-13, 13-5, 4-26 and 5-72, respectively.2. From comparison of these values with those previously found for non-senescent material (arginine, histidine and lysine values were not available) and from other considerations, it has been concluded tentatively thatthe onset of senescence was accompanied by an increase in the cyst(e)ine and possibly in the tyrosine content, and a decrease in the methionine content of the whole protein in the tissues.We wish to thank Mr D. S. Riceman for providing the leaf material used in this work.