The recent synthesis of a true glucose (“acrose”) by Fischer and Tafel, from acrolein (acrylic aldehyde) and also from glycerin, in conjunction with the additions to our knowledge of the constitution of dextrose and lævulose by Kiliani, &c., suggests fresh attention to the “aldehyde theory” regarding the synthetical formation of carbohydrate in green plants. It is now widely believed by vegetable physiologists that a glucose is produced in the first instance from CO 2 and H 2 O, but the nature of the intermediate changes is still uncertain.