The Mucilage of the Seed of White

IN comparison with the immense bibliographies of starch and cellulose for example, the literature of the gums and mucilages is scanty. This, doubtless, is due in part to the great commercial importance of the former, but a contributory cause may be sought in the practical difficulties involved in dealing with the latter. The gums Und mucilages are complex colloids which are not infrequently found to be mixtures of almost equally complex substances of closely similar physical and chemical properties. Separation of the constituents is consequently difficult, nor, when a separation has been achieved, is the characterisation of the components an easy matter. Nevertheless, increased knowledge of the chemical nature of such substances should be of interest to the plant biochemist and physiologist alike, and it is conceivable that the industrialist may also benefit ultimately as a result of such studies. Comparatively modern researches on the plant mucilages may be said to date from the end of the nineteenth century, when Gans and Tollens [1888] investigated the mucilage of quince. Similar products were examined by Yoshimura [1895] and von Bitto [1895], and this work was supplemented later by investigations of the mucilage of the prickly pear [Harlay, 1902], and of linseed [Hilger, 1903; Neville, 1913]. The early researches were concerned chiefly with the nature of the sugars produced on hydrolysis, and in the case of linseed mucilage, for example, Hilger reported xylose, glucose, arabinose and galactose as constituent sugars. Neville also isolated the "barium salt of an organic acid," but was not convinced that the acid was a constituent of the mucilage, regarding it as an impurity. This observation is of peculiar interest in view of the fact that the existence of uronic acids in such plant materials was at that time unsuspected. Re-awakened interest in the study of such plant products as pectin, hemicelluloses, gums and mucilages has followed the recognition of the wide occurrence of these acids, and recent investigations tend further to emphasise their importance. Galacturonic acid had been shown to be a constituent of