FORM OF ALEURONE GRAINS
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 77a.
DESCRIPTION OF ALEURONE GRAINS
The aleurone grains of curcas (Plate 77a, 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 77a, 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 77a, 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 77a, 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 77a, Fig. 5) are circular in outline, variable in form, and each grain contains from one to seven globoids.
In sesame seed (Plate 77a, 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 77a, 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.