46 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



the latter there is brought about an increase in volume in the outer layers, and this causes 

 a disintegration of the internal organization. The honey-combed structure was seen even 

 more clearly in the so-called artificial starch-grains which were prepared by condensation 

 of a starch-solution, when under the skin that covers the solution a layer of grains consisting 

 of starch was found. These grains, Biitschli recorded, show a characteristic honey-combed 

 structure, and in i:)olarized light behave exactly like natural starch-grains. Such artificial 

 starch-grains, ha\'ing a beautiful finely honey-combed appearance, are produced by freezing 

 a dilute starch solution. Biitschli holds that there can be no doubt about the chemical 

 nature of these artificially produced grains, and he also states that the structure of the 

 starch-grain seems incompatible with the theory of growth by intussusception, but entirely 

 in harmony with the theory of growth by apposition. On evaporation of a thin starch- 

 paste there arose at the outer edge of a droplet layers having lamellated structural char- 

 acteristics bearing a marked resemblance to the lamellae of the starch-grain. The origin of 

 the honey-combed structure Biitschli conceives to be due to a separation of water during 

 the concentration of the starch-solution, and to further loss of water by freezing. 



This investigation was supplemented by Biitschli (Botanisches Centralblat, 1896, 

 Lxviii, 213) with the conclusion that the structure of the spherocrystal of inulin and that 

 of the starch-grain is identical, and that both kinds of spherocrystals have arisen tlu-ough 

 a honey-combed method of building. He obtained spherocrystals of starch in this way: 

 A watery starch solution was prepared by boiling starch in water for 3 to 4 hours, when 

 the solution filtered until entirely clear. To the filtrate was added an equal volume of 

 a 5 per cent solution of gelatine, and the preparation was then evaporated almost to dry- 

 ness, when spherocrystals appeared. These crystals had a diameter of 0.05 mm. In polar- 

 ized light such crystals behaved exactly like the natural starch-grains, and the behavior 

 of the two towards iodine was similar, but solutions of chloride of calcium and of cliloral 

 hydrate acted differently on the natural and artificial starches. 



Biitschli agrees with Meyer (see page 47) as to the presence of a-amylose and 13- 

 amylose in natural starch, but he obtained only one of them in the form of artificial starch- 

 grains. 



Artificial starch-grains have also been prepared by Rodenwald and Kattein (Sitzungs- 

 ber. Kgl. pr. Akad. Wiss., 1899, xxiv, 628), Roux (Compt. rend., 1905, cxl, 440, 943, 1259), 

 Maquenne and Roilx (ibid., 1303), and St. Jentys (page 58). The former heated starch 

 in a solution of iodine and iodide of potassium in a sealed tube for 15 minutes at 130°. 

 A greenish liquid was formed which, they state, consisted essentially of a solution of starch- 

 iodide and some sugar. The clear filtrate, they record, became decolorized upon heating, 

 owing to the liberation of the vaporous iodine, which could be removed by a current of 

 steam. Upon slowly cooling the solution, a wliite substance separated in the form of 

 starch granules. These granules gave the characteristic blue reaction with iodine; they 

 were insoluble in water; they formed a thick paste on boiling; and they swelled and formed 

 a paste with potassium hydroxide. Roux found that by an incomplete degradation of 

 amylocellulose an artificial starch can be produced which has a cellular structure similar 

 to that of natural starch. These gi'anules, while giving the blue reaction with iodine, do 

 not gelatinize in hot water, and they therefore diflfer somewhat from both natural starch 

 and the artificial starch-grains of Rodenwald and Kattein (see pages 59 and 111). 



The honey-comb theory of Biitschli was opposed by Puriewitsch (Berichte d. deutsch. 

 Botan. Gesellsch., 1897, xv, 246). This experimenter used arrowi-oot, potato, wheat, and 

 camia starches, whereas Biitschli used only canna starch. Puriewitsch records that starch- 

 grains of arrowroot in the fresh condition show no honey-comb structure, nor is such a 

 structure apparent in starch-grains that have been in water for 24 hours. On slightly 

 swelling the grains, either by heating or by reagents, there is developed a quite definite 

 honey-comb appearance, but this Puriewitsch does not regard as an actual honey-comb 



