72 VEGETABLE HISTOLOGY. 



CHAPTER XVI. 

 ALEURONE GRAINS. 



Protoplasm exists both as active and inactive. In the active 

 state, as found in actively-growing cells, it exhibits vital phe- 

 nomena in a marked degree, but, as found in the cells of seeds, 

 tubers and thickened roots, it exhibits few signs of vitality, 

 contains comparatively little water and its condition approxi- 

 mates that of a solid. 



Ordinary protoplasm is formless; even under the highest 

 powers it exhibits no structure except the presence of numer- 

 ous very minute granular bodies called microsomes, the nature 

 and uses of which are not yet understood. It passes, however, 

 into several modifications which exhibit a more or less charac- 

 teristic structure. The most important of these is the chlor- 

 ophyll body. The amyloplasts, spoken of under starch, are 

 another form with structure. These are active forms of proto- 

 plasm. 



Alerone grains are a structural form of inactive protoplasm, 

 the use of which is to act as a reserve food material. Plants 

 lay up a store of food in various forms, one of which we have 

 studied, i. e., starch. Other non-proteid food materials are oil, 

 inulin, sugar. Some albuminous forms are also stored up, the 

 most important of which are aleurone grains. These are found 

 chiefly in seeds and most abundantly in oily ones. They are 

 usually rounded granules, often very small, but sometimes quite 

 large, as in Croton and Castor seeds and in the Brazil-nut. In 

 some cases the granules appear homogeneous in structure, as 

 in peony, almond, cherry and apple seeds; in other cases they 

 contain various substances, as oily matters, mineral crystals 

 and crystalloids, as in Brazil-nut, pumpkin and castor seeds, 

 walnut. 



The ground substance of aleurone grains is dissolved or 

 attacked by water, hence the latter is an unsuitable mounting 

 medium. Alcohol, glycerin or fixed oils have no solvent action 

 on the grains. Dilute alkalies readily dissolve the aleurone 

 grains except the mineral matter in them. 



CASTOR SEED. 



Kemove the hard seed-coat and make thin sections of the 

 endosperm. Mount one in strong glycerin and examine with 

 low and high powers. Not much will be made out with low 

 power. The cells will be seen to be crowded with rounded 

 granules, looking much like starch. 



Under high power, rounded or ellipsoid bodies, imbedded in a 

 finely granular matter fill the cells. These are the aleurone 



