DIV. I 



MORPHOLOGY 



31 



proteid substances occur as solid granules called ALEURONE GRAINS, 

 which are especially large in oily seeds (Fig. 23). They are formed 

 from vacuoles, the contents of which are rich in albumen, and harden 

 into round grains or, sometimes, into irregularly shaped bodies. The 

 albuminous substances of which they consist are mainly globulins ( 2S ). 

 A portion of the albumen often crystallises, so that frequently one 

 and occasionally several 

 crystals are formed within the ^ 

 aleurone grain. In aleurone 

 grains containing albumen 



FIG. 23. A, Cell from the endosperm of Ricinus 

 communis, in water ; B, isolated aleurone grains 

 in olive oil ; k, albumen crystals ; g, globoid. 

 (x 540. 



FIG. 22. Cell from the cortex of Dra- 

 caena rubra, filled with mucilagin- 

 ous matter and containing a bundle 

 of raphides, r. (x 1GO. After 



BCHKNCK.) 



FIG. 24. Part of a section of a grain of wheat, Triticum, 

 vulgare. p, Pericarp ; t, seed coat, internal to which 

 is the endosperm ; oZ, aleurone grains ; am, starch 

 grains ; n, cell nucleus, (x 240. After STRASBURGER.) 



crystals there may often be found globular bodies termed GLOBOIDS 

 (Fig. 23 g\ which consist of globulins combined with the calcium and 

 magnesium salt (phytin) of an organic phosphoric acid (phytic acid). 

 Crystals of calcium oxalate are also found enclosed in aleurone grains. 

 Free globoids are found in the cytoplasm of some seeds. In the 

 cereals the aleurone grains, which lie only in the outer cell layer of 

 the seeds (Fig. 24 al\ are small, and free from all inclusions; they 

 contain neither crystals nor globoids. As the outer cells of wheat 



