Botany. — "Cri/staII!sr<J Stardi". By Prof. Dr. M. W. BeijeriKck. 



The fact tliat starch crystallises easily is not generally known. It 

 is true that Arthur Meykr supported the view that the starch grain 

 is a sphero-crystal, ') but convincing tignres he does not give; his 

 considerations are hypothetical and not decisive as he did not make 

 any microscopical examination on soluble starch. Moreover, - the 

 highest temperature used by him was but 145° C, and he conti- 

 nued the heating iiol long enough. 



Most species of starch, such as that of potato, wheat, barley, rye, 

 rice, maize, behave as follows. 



When a lO"/» solution, after previous boiling and gelatinising in 

 distilled water, is heated during tifteen minutes or half an hour at 

 150° to 160" C the grains dissolve to a perfectly clear, transparent 

 liquid, in which, at slow cooling, a crystalline deposit sets off, 

 consisting of very fine needles, which are either isolated or united 

 in groups of various shapes, not seldom resembling natural starch, 

 and which must undoubtedly be considered as crystallised starch 

 on account of their behaviour towards diastase and chemical reagents. 



The free needles, measuring but few microns or parts of microns, 

 make the impression of an amorphous sediment. The groups, formed 

 by longer needles have the shape of corn-sheaves or bundles of 

 ai'rows (bolidesms) ; or of discs (bolidiscs), reminding in size and 

 form of the red blood-cells; or they are more or less regular globules 

 (spherites or sphero-crystals), from whose surface, however, here 

 and there project the crystal needles. 



Potato starch is very well apt to produce bolidesms and sphero- 

 crystals ; it is suftic'ent to iieat to 150° C, during a quarter 

 of an hour, a 107o solution in distilled water, previously boiled 

 and gelatinised. After being kept 24 hoius in a cold room 

 loose needles, bolidesms or sphero-crystals are precipitated, and 

 their crystalline nature is easily observable. What circumstances 

 determine the union of the needles to bundles is not yet well 

 known, but certainly slowness of crystallisation favours it, and the 

 concentration has also some influence. Not seldom the whole deposit 

 consists of a magnificent mass of sphero-crystals (Fig. 1). The discs, 

 to which I shall return presently, are formed from potato starch 

 at a somewhat lower temperature than the needles mentioned here. 



') Untersuchungen iiber Staikeköiner, Jena, i895 Beitrage zur Kenntnis der 

 Starkegallerlcn, Kolloidcliemisclie Beihefte Bd. 5, Pag. 1. 1913. The observations 

 and opinions of Bütschli, Untersiiclinngon iiber Slrukturen, Pag 283, Leipzig l.s&S, 

 are obscure. 



