1. P. B. Medawar, A unsolved problem of biology. Reprinted in “The Uniqueness of the Individual,” Methuen, London (1957).
2. H. W. Woolhouse. Senescence processes in the life cycle offlowering plants. Bioscience, 28:25 (1978).
3. C. W. Minot, The Problem of Age, Growth and Death, G. P. Putnam’sSons, London. (1908).
4. W. Pfeffer, The Physiology of Plants, Volume 2 Transi. by A. J. Ewart, Clarenden Press, Oxford (1903).
5. D. W. Thompson, On Growth and Form. 2nd Edition Cambridge University Press, (1942).