The high prices commanded by grain and breadstuffs in Europe, renders the present a remarkably favorable time to ascertain what can be done in this branch of tropical agriculture; for should the potato disease return, or this root be less extensively planted than hitherto, starch must maintain a high price, and it will be worth ascertaining whether some of the superior starch-producing plants of the tropics might not be cultivated to such an extent as to supply the English market, and thus be at once profitable to the colonies and advantageous to the mother country.

Before entering on such a cultivation, however, various points require investigation.  We ought to be able to answer such questions as the following:—­

1.  What differences exist between the characters of starch produced by different plants?

2.  What are the qualities or properties that lead manufacturers—­calico printers for example—­to prefer one variety to another?

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.  What 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 imperfectly 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 as 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 distinguishable.  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 cover them with a drop of aqueous solution of iodine, which renders them gradually blue and opaque.  When the difference in size and form between the globules of different species is considerable, as between the Tous les mois 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.