300 



MANUAL OF BOTANY 



in large proportion in amorphous form. In most cases, how- 

 ever, it is deposited in the form of grains of definite shape and 

 sometimes of complex character. These grains are known as 

 aleurone grains. They consist of mixtures of proteids belonging 

 to the globulin and albumose classes, which show considerable 

 differences in solubihty. In most cases they can be seen to 

 lie in a coarse meshwork of protoplasm. They are esp^ially 

 characteristic of the cells of the interior of the seed, where they 

 are reserve nitrogenous materials for the use of the embryo 

 during germination. 



The alem-one grains vary very much in size and shape. In 



Fui. 6,54. 



Fig. 654, Cell from the emlosperm or albumea of the seed of the Castor-oil 

 plant (Jiicinus commimh) in dilute glycerine, showin'g large transparent 

 proteid or aleurone grains, with crystalloids and globoids embedded in 



them. After Sachs. Fn/. 655. Cells of a very thin section through a 



cotyledon of the embryo in a ripe seed of the common Pea (I'launi 

 saUviim). a, a. Aleurone grains, si. Starch granules, i, i. Intercellular 

 spaces. After Sachs. 



the Pea they may be seen as very small round bodies lying in the 

 same cells as starch grains {fig. 655). In the Lupin they are 

 larger, and occur in conjunction with oil, but not starch. In 

 both these cases they show no structure. In the Castor-oil seed 

 and in that of the Brazil nut they differ from the simple forms 

 described. The larger part of the aleurone grain is occupied by 

 a crystalline portion, known as the crystalloid. This, like the 

 grain itself, is proteid in character. There is present also in 

 these grains a rounded aggregation of mineral matter, a double 

 phosphate of calcium and magnesium, which is termed the 

 globoid (fig. 654). 



