18 I. THE COMPOUND MICROSCOPE STRUCTURE OF STARCH. 



in water. In this mountant the starch grains appear on the 

 average smaller ; their lamination can scarcely be recognised ; the 

 inner hollow and the clefts are wanting. These were formed, 

 therefore, as the result of the swelling of the grain under the 

 influence of the water. 



Arrowroot Starch. W T est Indian arrowroot, also called in 

 short arrowroot, prepared from the rhizome of various species of 

 Maranta, especially of M. arundinacea, is easy to obtain in shops. 

 Observed in water, the grains show great similarity to those of 

 the potato; but they are usually less clearly and more uniformly 

 laminate, somewhat more rounded, on the whole smaller, also 

 more uniform in their size. At the position of the hilum is usually 

 found a cleft, in the form of a wide-open V. 



Wlieat Stored Wheat meal shows the layering very badly ; 

 as, on the whole, most favourable, we select for observation the 

 starch grains of Triticum durum. We halve the grain of wheat 

 with the pocket knife, scrape off a little substance from the cut 

 surface, and put it in the drop on the object-slide. The large 

 starch grains are circular, discoidly flattened, and regularly 

 laminate (Fig. 7, A); but the layers are usually difficult to see. 

 In many grains they will, however, be 

 recognised, as well as the central hilum. 

 Occasional grains show also upon their 

 surface a beautiful reticulation, more or 

 less regular, and occupying only a small 

 portion of the surface of the grain. This 



FIG. 7. Wheat starch from . . . . , , i r 



Triticum durum. A, a large, reticulation is formed by a network ot 

 B, small grains. small ridges, and, similarly, the meshes 



represent very shallow hollows. As a characteristic appearance, 

 there will be found in the preparation, besides the large grains 

 and almost without transition sizes, small grains with clear rosy 

 hilum, but without recognisable lamination. Several such grains 

 are represented at B. In many preparations compound grains 

 are not rare; but usually they are sought for in vain, as they 

 have fallen into their component grains. 



Oat Starch. We shall best study the starch of the oat (Avena 

 sativa) if we halve an oat grain, taking a little of the contents for 

 observation under water. Compound grains are here met with in 

 great beauty, as represented in the adjoining figure. The size of 

 these compound grains varies, and similarly also the number of 

 constituent grains entering into their composition. Fig. 8, A, 



