780 STARCHES OF ZINGIBERACE^. 



The grains vary in dze from 7.5 to 64/i. The common size is about 44 by 22/x in length and breadth. 



Poluriscopic Pruperlies. The figure is extremely eccentric, very tlistinet, but not sharply 

 defined. Its lines are apt to be broad, of nearly uniform width, but not clear-cut. As a rule only 

 one or two lines are seen. When only one is present it follows closely the longitudinal axis of the 

 grain; but when there are two they are marginal, the part of the grain corresponding to the longi- 

 tudinal axis being bright. 



The degree of -polarization is fair. It varies according to the position of the grain. It is highest 

 when the grains are observed on end or edge. It varies in different grains, is almost absent in eroded 

 parts, and is higlier when grains are overlapped. 



With selenite the quadrants are fairly well defined. Usually only one or two quadrants are 

 visible, sometimes one and parts of two, and rarely parts of four. The quadrants tend to be quite 

 regular in shape, but are usually unequal in size. The colors are generally fairly pure. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains color fairly deeply a blue- 

 violet; with 0.125 per cent solution the color is light at first, but deepens fairly rapidly. After heat- 

 ing until the grains are completely gelatinized, the solution reacts very lightly and the grains deeply 

 on the addition of iodine. After boiling for 2 minutes, the solution is much more deeply colored, 

 but the grain-residues only slightly. With an excess of iodine, some grains react a dark blue with a 

 violet-colored capsule; others show but little of the blue-reacting substance and a violet-colored 

 capsule. 



Staining Reactio7is. With gentian violet the grains begin to stain at once, but the distal end 

 is much more deeply stained than the rest and a very sharp line of demarcation usually exists be- 

 tween the two parts. After 30 minutes they are fairly deeply stained. 



With safrantJi the grains begin to stain at once rather lightly, but even after 30 minutes they 

 are lightly colored, the distal end more deeply than the proximal, although there is not so much 

 difference as when gentian violet is used. 



Temperature Reaction. The temperature of gelatinization is 73.3 to 74.4 C, mean 73.85. 



Effects of Various Reagents. With chloral hydrate-iodine reaction begins in most grains in 30 

 seconds and is over in 2 minutes. The hilum and lamella are obscured. The distal end becomes dark 

 and begins to swell somewhat smoothly, appearing like a cap fitted on the end of the grain. This 

 cap is probably freshly deposited starch. The grains now become dark thi-oughout the distal end, 

 and irregular points on the periphery darken, and swelling and gelatinization proceed from the 

 distal end along the margin of these points, usually along only one side, continuing around the 

 proximal end before extending upward along the other side. Wlien the process has progressed all 

 around the mai-gin, the central portion is invaded and the outer part of the grain becomes a capsule, 

 which contains a mass of gelatinized starch. The gelatinized grains show a smooth, rounded distal 

 end, separated from the swollen cap previously noted. The grain is swollen, and many fine lamella 

 are seen, such as would appear in an ungelatinized grain. At the distal end there may be one or 

 more elongated sacculations, and rarely the whole margin may show these irregular protrusions. 



The reaction with chromic acid begins in 20 seconds and is over in 2 minutes. The hilum swells 

 quickly and protrudes from the end of the grain, the upper part undergoing solution. The lamellae 

 are very distinct. The cap-hke part at the distal end of the grain separates from the rest, becomes 

 as a rule finely granular and swells, and finally is dissolved sometimes in a manner similar to thatof 

 the major part of the grain. The lamella appear to be detached one by one, but there is no definite 

 separation of crescents as in certain starches. This process continues until the grain is entirely 

 dissolved. 



With pyrogallic add in 2 minutes there is a reaction in a few grains, and in 30 minutes all show 

 some reaction. After 45 minutes there is practically no further change; the preparation is dried at 

 this time. The hilum and lamellae are both very clear. The hilum swells slightly and the portion 

 of the grain around it becomes rapidly striated. A line of demarcation in the form of a gradually 

 widening, clear space appears between the cap-like end and the body of the grain, and small fissures 

 extend upward into the grain from the distal end. The main jiart of the grain appears to be grad- 

 ually transformed into a gelatinous mass, the inner part going first, the outer appearing as a very 

 distinct, homogeneous wall, which becomes gradually thinner and clearer. The gelatinized grains 

 are fairly large, crumpled, and wrinkled. 



Reaction with ferric chloride begins in a few grains in 45 seconds and is completed in 5 minutes. 

 The hilum and lamella; are not visible. The hilum and near-by parts swell greatly with irregular 



