STARCH-PRODUCING PLANTS. 333 



3. For culinary purposes, and as an article of diet, what 

 qualities or characters obtain a preference ? 



4. Can the starches from different plants be distinguished from 

 one another by distinct and well marked characters, so that the 

 substitution of a less esteemed variety for a more esteemed one, 

 or the adulteration of a high priced variety with a cheaper one, 

 could be readily detected ? 



5. AVhat plants produce the most esteemed varieties ? 



6. What plants produce it in the largest quantity ? 



7. "What plants produce the largest yield per acre ? 



8. From what plants is it most easily manufactured ? 



9. Is the process attended with any particular difficulties that 

 ought to deter the East and West India planters from engaging 

 in it ? 



In the following observations (continues Dr. Shier) I shall be 

 able to reply to several of these questions, especially those capable 

 of being settled in the laboratory. On other points, particularly 

 those relating to the returns per acre, I am at present but imper- 

 fectly informed, in consequence of the limited extent to which these 

 plants have hitherto been cultivated in this colony (Demerara), 

 and from the total absence of authentic data regarding the amount 

 of yield. 



Characters of starch produced from different plants. Starches 

 from different plants are best distinguished from one another by 

 examination under a good miscroscope. The grains or globules 

 may be examined either a,s transparent or opaque objects ; and 

 although in the same species there are considerable differences in 

 size and form, the different kinds are, on the whole, quite dis- 

 tinguishable. One of the best ways of examining the form of 

 the globules under the microscope, is to lay them on a plate of 

 glass and co\ r er them with a drop of aqueous solution of iodine, 

 which renders them gradually blue and opaque. When the dif- 

 ference in size and form between the globules of different species 

 is considerable, as between the Tous les inois starch and cassava 

 starch, or even between the arrowroot starch and cassava starch 

 frequently used to adulterate it, it is not difficult, with a little 

 practice, to detect the fraud. 



TABLE ILLUSTRATIVE OF THE SIZE AND FORM OF THE STARCH GLOBULES 

 OF VARIOUS PLANTS. 



1. Tous-les-inois (Canna coccinca). Grown in Grenada, 1-300 to 1-2,000 of 

 an inch ; general size, 1-500 ; form of the globules, large, elliptical and ovate, 

 and remarkably transparent. 



2. Ditto ditto (species unknown). From a plant grown in the garden of the 

 Hon. J. Croal, Georgetown, but gathered before the root was fully ripe; globules 

 spherical, shortly ovate and elliptical ; size, from 1-600 to 1-1,600 ; general 

 size, 1-800, 



3. Buck Yam (Dioscorea triphylla). Grown on the banks of thu Demerara 

 Eiver. Form of globulrs, elliptical, often truncated at one end, so as to be 

 mullar-shaped, some pear-shaped; length, twice the width; size, 1-600 to 

 1-2,000; general size, 1-800. 



4. Common Yam (D. saliva). Grown on No. 1 Canal, Demerara River. 

 Elliptical, some long elliptical; size, 1-700 to 1-2,OCO; general size, 1-1,000. 



