The conditions for the formation of gels from banana extracts were studied. Gels were obtained with extracts more alkaline than pH 7.0 with very small quantities of calcium, strontium, and barium salts, the gel formation with these salts decreasing in the indicated order. In solutions more acid than pH 6.0, no gels were obtained with these salts. Magnesium, lithium, and sodium salts did not cause gel formation either in acid or alkaline solutions. Pancreatine gave a gel on incubation with banana extract at pH 5.0. The gel-forming property of banana extracts was destroyed on boiling.

A number of different methods of treatment of unripe and ripe bananas for the purpose of obtaining and studying sucrolytic and amylolytic enzymes are described. No conclusive evidence of the presence of an amlyase could be obtained in any of the preparations. The sucrase of unripe and ripe bananas was studied more extensively. With ripe bananas, both soluble and insoluble sucrase preparations were obtained. Conditions for converting the soluble into an insoluble form were found. The actions of the sucrase preparations as far as the hydrogen ion concentration for maximum action and the time-action relation are concerned are similar to the behavior of the yeast and the potato sucrase.

The saccharogenic enzymes present in potato juice were studied. The actions were followed upon the substances present in the juice and upon added sucrose, maltose, and soluble starch. Sucrase and amylase were found to be present in the juice. No indication of a maltase was obtained. The sucrase showed optimum conditions for action at pH 4 to 5, the amylase at pH 6 to 7, both upon the starch present in the juice and upon added soluble starch. The action of a yeast sucrase preparation upon the juice showed the presence of sucrose (or raffinose) in a concentration of the order of magnitude of 1 per cent.