MORPHOLOGY 



71 



Crystals of calcium oxalate are also found enclosed in the aleurone 



A, Cell from the endosperm of Bicinits 

 communis, in water ; B, isolated aleurone grains 

 in olive oil ; /c, albumen crystals ; g, globoid, 

 (x 540.) 



The seeds of Hicinus (Fig 78) furnish good examples of aleurone grains with 

 enclosed albumen crystals and glo- 

 boids. The aleurone grains them- 

 selves lie embedded in a cytoplasm 

 that is rich in oil. In the cereals 

 the aleurone .grains which lie only in 

 the outer cell layer of the seeds 

 (Fig. 79, al) are small, and free from 

 all inclusions ; they contain neither 

 crystals nor globoids. As the outer 

 cells of wheat grains contain only 

 aleurone, and the inner almost ex- 

 clusively starch, it follows that flour Fig. 78. 

 is the richer or poorer in albumen, 

 the more or less completely this outer 

 layer has been removed before -the 

 wheat is ground. From the inner layers finer and whiter flour can be made ; 

 while more nourishing flour is obtained from the outer layers. 



Reactions for aleurone are the same as those already mentioned for the albuminous 



substance of protoplasm. Treat- 

 ment of a eross-seetion of a grain 

 of wheat (Fig. 79) with a solution 

 of iodine would give the aleurone 

 layer a yellow-brown colour, while 

 the starch layers would be coloured 

 blue. 



Albumen Crystals. — Crystals 

 of this nature are especially fre- 

 quent in aleurone grains (Fig. 78). 

 They have previously been men- 

 tioned as occurring in the chroma- 

 tophores. In the illustration of 

 the leucoplasts of Phajus graiidi- 

 folius (Fig. 77), the rod-shaped 

 crystals are represented as light 

 stripes (in B and E). In the 



green Algae, the angular, strongly 

 -Part of a section of a grain of wheat, Triticum „ ,. , -.. . . . .. 



p, Pericarp;/, seed coat, internal to which refractive bodies lymg in the 

 is the endosperm ; aZ, aleurone grains ; cm, starch chloroplasts and surrounded by a 

 grains ; n, cell nucleus, (x 240.) ring of starch granules are albu- 



men crystals. A good example 

 of these bodies, known as pyrenoids or amylum centres, may be seen in 

 the green bands of Spirogyra (Fig. 235). Albumen crystals may also occur di- 

 rectly in the cytoplasm ; as, for instance, in the cells poor in starch, in the peri- 

 pheral layers of potatoes. Albumen crystals are sometimes found even in the 

 cell nucleus. This is particularly the case in the Toothwort (Lathraea, 

 squamaria). Albumen crystals usually belong either to the regular or to the 

 hexagonal crystal system. They differ from other crystals in that, like dead 



