/e 



-3- 



Schimper supported the hypothesis of the starch- 

 grain being a crystalline body upon the basis of the cohesive 

 and optical properties which distinguish amorphous from cryst- 

 alline structures, and he studied with some care the analogies 

 between the starch-grain and ordinary sperocrystals. He observed 

 that the grains break more easily tsansversely than pf«i 

 parallel to the lamellae, and that such a peculiarity had not 

 been noted in amorphous bodies, because the absence of 

 regularity of arrangement of the molecules m.akes h% them 

 split Irregularly when crushed. A filamentous crystalline 

 aggregate when crushed, he observes, separates in lines parallel 

 to the bundles, because the force which binds the latter is 

 more easily overcome than the cohesion of the molecules of the 

 individual crystals. The striated nature of the broken faces 

 shows, he staes, hov/ the fibers are separated, and that the 

 starch-grains exhibit this same phenom.enon, thus resembling 

 radio-fibrous crystalline aggregates and differing from 

 amorphous bodies. The polariscopic characteristics he found 

 to agree entirely with the cohesive properties, and like them. 

 to be owing to the crystalline nature of the starch-grain. 

 Viewed in polarized light the "interference figure" is such 

 as starch-grains should exhibit if they are composed of bundles 

 of crystalline uniaxial or rhomboidal elements, and virould split 

 up transversely to the lamellae. 



Schimper states that Baily and also von Lang reached 

 this conclusion; and that Mohr ' s assertion that the arms of 

 the interference cross always run perpendicular to the lamellae 

 holds good only for a regular centric or spherical structure, 

 as they often intersect eccentric grains at a very sharp angle. 

 In regular centric spherical structures, as well as in the axes 

 of eccentric ones, the doubly refractive elements are straight 

 and extinguish the light in its entire length; the lateral 

 parts of the eccentric grains Jsehave differently; as shown by 

 the bundles and the fissures, which described a cxor-ve, and 

 according to this satisfy the conditions for extinguishing 

 the light in more or less of their length. Tliese character- 

 istics, he writes, like those of cohesion, can be attributed 

 only to the fact that starch-grains consist of crystalline 

 bundles which run parallel to the lamellae. Starch-grains, he 

 notes, differ from ordinary spherical crystals in their property 

 of s'.velling, and he proposes to distinguish spherocry stals and 

 all crystalline bodies which possess this property as crysta- 

 lloids. Schimper states that one may conclude that starch- 

 granules consist of radially arranged crystalloids; that the 

 crystallized starch-substance has the formula ^6^^10^5' that 

 there are probably several isomers; that various conditions 

 can be cited to prove that starch-crystals always appear in 

 aggregate bundles and never singly; and that the conditions 

 which account for the occurrence of aggregates are difficult 

 solubility, with low power of crystallization, and the viscosity 

 of the solution which crystallization takes place, and that 

 any one of these factors may in some cases suffice. 



