BOTANY 



super-heated water at 140 3 -150 C. Starch swells very readily at ordinary 

 temperatures in solutions of potassium, or sodium hydrate. Heated without 

 addition of water, i.e. roasted, starch becomes transformed into dextrin, and is 

 then soluble in water and correspondingly more digestible. The glutinous starch 

 of varieties of Rice and Millet (Oryza saliva, var. ylntinoxx, Xr</hii>/i nil'jurc, 

 ylutinosum) is in the completely unswollen condition coloured brown with iodine ; 

 when swollen by a dilute solution of iodine, it takes a red, wine-red, or purple 

 colour. According to 0. BUTSCHLI ( m ) it consists of amyloerythrin, a carbo- 

 hydrate resembling starch. In polarised light, starch grains, like inorganic 

 sphferites, show a dark cross. This appearance is usually referred to the doubly 

 refractive nature of the elements of which the starch grain is constructed. 



The amount of starch contained in reservoirs of reserve material 

 is often considerable ; in the case of potatoes 25 per cent of their 

 whole weight is reserve starch, and in wheat the proportion of starch 

 is as high as 70 per cent. The starch flour of economic use is derived 

 by washing out the starch from such reservoirs of reserve starch. In 

 the preparation of ordinary flour, on the contrary, the tissues con- 

 taining the starch are retained in the process of milling. 



Aleurone. Aleurone or proteid grains are produced in the seeds 

 of numerous plants, especially in those containing oil. 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, accord- 

 ing to A. TSCHIKGH and H. KRITZLER ( 8 ), mainly globulins. 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 crystals there may often be 

 found globular bodies, termed GLOBOIDS, which, according to PFEFFER 

 ( 9 ), consist of a double phosphate of magnesium and calcium in 



combination with some organic 

 substances. Crystals of calcium 

 oxalate are also found enclosed 

 in aleurone grains. 



Jt 



A 



ff The seeds of Ricinus (Fig. 83) 



furnish good examples of aleurone 

 grains with enclosed albumen crystals 

 and globoids. The aleurone grains 

 themselves lie embedded in a cyto- 

 plasm that is rich in oil. In the 

 FIG. 83. A, Cell from the endosperm of Ricinus cereals the aleurone grains which lie 

 wnmttni*, in water; 1'. isolated aleurone grains Q ^ JQ t j )e Quter ^ j of the 



in olive oil ; I:, albumen crystals ; a, glolioid. . _. ,. 11 i < 



seeds (Fig. 84 at) 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 exclusively starch, it follows that flour 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 



