Much attention has been given to the study of the special parts of the aleurone grains, but one of the most important diagnostic characters has been overlooked, namely, that of comparative form. For the purposes of comparing the forms of different grains, they should be mounted in a medium in which the grain and its various parts are insoluble. Oil of cedar is such a medium. The variation in form and size of the aleurone grains when mounted in oil of cedar is shown in Plate 77_a_. DESCRIPTION OF ALEURONE GRAINS The aleurone grains of curcas (Plate 77_a_, Fig. 1) vary in form from circular to lens-shaped, and each grain contains one or more globoids. The globoids are larger when they occur singly. In sunflower seed (Plate 77_a_, Fig. 2) the grains vary from reniform to oval, and one or more globoids are present; many occur in the center of the grain. The aleurone grains of flaxseed (Plate 77_a_, Fig. 3) resemble in form those of sunflower seed, but the grains are uniformly larger and some of the grains contain as many as five globoids. In bitter almond (Plate 77_a_, Fig. 4) the aleurone grains are mostly circular, but a few are nearly lens-shaped. A few of the large, rounded grains contain as many as nine globoids; in such cases one of the globoids is likely to be larger than the others. The aleurone grains of croton-oil seed (Plate 77_a_, Fig. 5) are circular in outline, variable in form, and each grain contains from one to seven globoids. In sesame seed (Plate 77_a_, Fig. 6) the typical grain is angled in outline and the large globoid occurs in the narrow or constricted end. The aleurone grains of castor-oil seed (Plate 77_a_, Fig. 7) resemble those of sesame seed, but they are much larger, and many of the grains contain three large globoids. When these grains are mounted in sodium-phosphate solution, the crystalloid becomes visible. TESTS FOR ALEURONE GRAINS Aleurone grains are colored yellow with nitric acid and red with Millon’s reagent. The proteid substance of the mass of the grain, of the globoid, and of the crystalloid, reacts differently with different reagents and dyes. The ground substance and the crystalloids are soluble in dilute alkali, while the globoids are insoluble in dilute alkali. The ground substance and crystalloids are soluble in sodium phosphate, while the globoids are insoluble in sodium phosphate. Calcium oxalate is insoluble in alkali and acetic acid, but it dissolves in hydrochloric acid. [Illustration: PLATE 77_a_ ALEURONE GRAINS 1. Curcas (_Jatropha curcas_, L.). 2. Sunflower seed (_Helianthus annuus_, L.). 3. Flaxseed (_Linum usitatissimum_, L.). 4. Bitter almond (_Prunus amygdalus_, _amara_, D.C.). 5. Croton-oil seed (_Croton tiglium_, L.). 6. Sesame seed (_Sesamum indicum_, L.). 7 and 8. Castor-oil seed (_Ricinus communis_, L.).] CRYSTALS