MORPHOLOGY 



77 



flour can be made : while more nourishing Hour is obtained from the outer 

 layers. Reactions for aleurone are the same as those already mentioned for 

 the albuminous substance of protoplasm. Treatment of a cross-section of a grain 

 of wheat (Fig. 84) with a solution of iodine would give the aleurone layer a yellow- 

 brown colour, while the starch layers would be coloured blue. 



ALBUMEN CUYSTALS. Crystals of albumen are of relatively frequent occurrence 

 in vegetable tissues and are often found in aleurone grains (Fig. 83). Their 

 appearance in the seed of Ricinus has been described above, and especially large 

 crystals are found in the endosperm of the Brazil nut (BertlmHrtiti. ov/Vs^ i 



if 



Ki<;. S4. Part of u section M!';I -rain ol' wheat, Tfitii-mn 

 i- nil/are, p, Pericarp ; t, seed coat, internal to which 

 is the endosperm; al, aleurone grains; mn, starch 

 grains ; //, cell nucleus, (x 240.) 



KlO. 85. Cell I'r the cortex 



of Drvaienti i-ubrn, tilled 

 with mucilaginous matter 

 and containing a bundle 

 of raphides. /. (x HiO.) 



ing to the Lecythidaceae. They have previously been mentioned as occurring in 

 the chromatophores. In the illustration of the leucoplasts of Phajus grandifolius 

 (Fig. 82), the rod-shaped crystals are represented as light stripes (in B and E). 

 Albumen crystals may also occur directly in the cytoplasm ; as, for instance, in 

 the cells poor in starch, in the peripheral layers of potatoes. Albumen crystals 

 are sometimes found even in the cell nucleus. This is particularly the case in the 

 Toothwoi t (Lathraea squamaria], and in many Scrophulariaceae and Oleaceae ( 70 ). 

 Albumen crystals usually belong either to the regular or to the hexagonal crystal 

 system. They differ from other crystals in that, like dead albuminous substances, 

 they may be stained, and also in that they are capable of swelling by imbibition. 

 Subjected to the action of water or a dilute solution of caustic potash, they at first 

 increase in size without losing their crystalline outline. 



