1. Allott, E. N.,Richter’s Organic Chemistry, 1934, 314.
2. Barber, C. A.,Mem. Dept. Agric. Bot. Ser., 1914,7, 16.
3. Biffen, R. H.,Jour. Genetics, 1916,5, 225–28.
4. Ganong, W. F.,The Living Plant, 1913, 118.
5. Haberlandt, G.,Physiological Plant Anatomy, translated by Drummond, M., 1928, 107–8.