HARDWICKE'S SCIENCE-GOSSIP. 



221 



the present (lay in connection with the recent 

 Adulteration Act is very great, and with the 

 aiicroscope it would be easy to go through dozens 

 of different kinds of starches and And differences 

 between almost every kind, even much greater than 

 between the Tous-lcs-Mois and potato. About 

 fifty different kinds of starches have recently come 

 under my examination, many of which I have 

 sketched with the aid of camera lucida to an exact 

 scale of measurement. 



Fig. 122. Tous-les-Mois (polarizeJ). 



The chief characteristics to be noted in making 

 an examination are : 1. Size and shape of granules, 

 using micrometer scale. 2. Position, size and 

 shape of nucleus, noting concentring or eccentricity 

 of lamination. 3. Effect of polarization with or with- 

 out selenite. 







Fig. 123. Starch grains of Yam. Rice, and Maize, 

 250 cliain. x 6. 



f With regard to the size of the granule, though a 

 single cell of any vegetable substance will contain 

 granules according to progress of development, 

 from the very smallest size upwards, yet few 

 varieties of starches will be found to average the 

 same size. Thus, a single cell of potato will 

 contain granules from the toW to the ^o of an 

 inch ; arrowroot will vary between the toVo and 

 s£o of an inch ; wheat. rarely exceeds the xoVo ; 

 and rice will not exceed the soV'tt, being usually 

 about the ^ of an inch. 



The shape of the granules, though more uniform 

 than the size in a given starch, is variable. Potato 



starch might be described as ovate, but individual 

 granules may be rounded or mussel-shaped. 



Pice starch is usually angular, but many of its 

 granules are round. 



Yam starch approaches nearly to the triangular 

 form. 



So that both as to form and size, though it would 

 be rash in most cases to pronounce with certainty 

 the name from a single granule, yet we should be 

 quite justified in doing so from the form and size of 

 any sample. 



The position and shape of the nucleus taken in 

 connection with the lamination afford a valuable 

 means of distinguishing starches. In lenticular 

 grains, as in wheat, the layers grow in connective 

 circles with central lenticular nucleus. But if as in 

 potato starch the growth is in one direction, the 

 layers with the exception of the one nearest the 

 nucleus are eccentric to the nucleus, which is itself 

 usually globular. 



Fig. 124. Potato- granules, 

 250 diam. x 6 (eccentric 

 lamination). 



Fig. 125. Starch of French 

 Lentils (concentric lami- 

 nation). 



In the starch of Indian corn the nucleus is 

 usually very distinct, and the lamination in this and 

 several other kinds so indistinct that it is only with 

 the aid of high powers and the use of magenta 

 solution that they can be at all distinguished. 



On the other hand, Natal arrowroot can be 

 readily distinguished even from other arrowroots by 

 the special clearness of its lamination. Erom this 

 fact, it has been frequently mistaken for potato 

 starch, though it never need be, for apart from the 

 wide difference in size, the granule being only two- 

 thirds that of the potato, and the difference in shape 

 of nucleus, the fact that the nucleus in the potato 

 granule is usually at the smaller end, and that of 

 arrowroot at the broader end, is sufficiently charac- 

 teristic to prevent any confusion. 



The characteristic markings produced by the 

 polarization of starch are familiar to all micro- 

 scopists, usually assuming the form of a cross or 

 the letter X, the nucleus being the point from 

 which radiation proceeds. The effect produced by 

 polarization naturally varies considerably, according 

 to the form of granule and other causes. Some 

 specimens of the same kind polarize much more 

 than others— a fact which has led to much error. 

 Thus almost all authorities state that wheat and 

 rice starches do>ot T polarize at all, the fact being 



