17. Tannia (Caladium sagittifolium).—Grown at the Lodge. Globules not so truly spherical as the foregoing, but range and size the same.
18. Wheat (Triticum sativum).—Locality unknown. Form of globules, spherical and slightly elliptical, some very small; range, 1-2,000 to 1-6,000, the former the general size.
19. Maize (Zea Mays).—Grown in the colony, but locality uncertain. Globules, approaching to spherical, much aggregated; range, 1-2,000 to 1-4,000; general size, 1-3,000.
From an inspection of this list, it does not appear that the species would be easily distinguishable, and it is not easy briefly to describe the differences; in practice, however, and especially when the observer has a number of pure and authentic specimens before him, to have recourse to as standards of comparison, the discrimination is by no means difficult.
Specific gravity of starch derived from various plants.—Of many bodies the determination of the specific gravity is one of the best modes of distinguishing the purity. With the view of ascertaining whether the different varieties of starch have all the same density, as has been asserted by some, trials were carefully made of as many specimens as I could procure. The results are embodied in the following table:—
| TABLE No. I.—DENSITY OF STARCH DERIVED FROM VARIOUS PLANTS. | |||
| Names of Plants | Density | Tem. at time of Obs. °F. | Remarks |
| 1. Bitter cassava | 1.4773 | 87. | Grown in the colony and prepared in the Colonial Laboratory. |
| 2. Tannia | 1.4773 | 87. | Ditto ditto |
| 3. Arrowroot | 1.4772 | 86.25 | Ditto ditto |
| 4. Arrowroot | 1.4748 | 86.25 | Ditto ditto |
| 5. Common yam | 1.4733 | 83.25 | Ditto ditto |
| 6. Sweet potato | 1.4718 | 85.75 | Ditto ditto |
| 7. Arrowroot | 1.4717 | 82.75 | St. Vincent's, commercial |
| 8. Arrowroot | 1.4701 | 84.75 | Grown in the colony and prepared in C.L. |
| 9. Tous les mois | 1.4698 | 85.25 | Ditto ditto |
| 10. Sweet cassava | 1.4692 | 86.5 | Ditto ditto |
| 11. Wheat starch | 1.4632 | 85. | Commercial, of English manufacture |
| 12. Plantain | 1.4615 | 85.75 | Grown in the colony and prepared in C.L. |
| 13. Tous les mois | 1.4611 | 84.25 | Grenada, commercial |
| 14. Barbados yam | 1.4607 | 83.5 | Grown in the colony and prepared in C.L. |
| 15. Irish potato | 1.4589 | 84.75 | Tubers from Belfast; prepared in C.L. |
| 16. Guinea yam | 1.4581 | 84.2 | Grown in the colony and prepared in C.L. |
| 17. Potato | 1.4561 | 84. | Commercial |
| 18. Buck yam | 1.4489 | 81.25 | Grown in the colony and prepared in C.L. |
| 19. Arrowroot | 1.4443 | 85.5 | Barbados, commercial |
| 20. Arrowroot | 1.4158 | 86.25 | Bermuda, ditto |
| 21. Maize | 1.4109 | 85.5 | Grown in the colony and prepared in C.L. |
From this it will be seen that the order of density does not correspond with the order in any of the other tables. Probably those specimens prepared from dry seeds, such as wheat and maize starch, which, as commercial articles at least, are less pure than those prepared from recently dug roots, have also the lowest density.
Hygroscopic properties of starch produced from different plants.—Such of the specimens as are marked in the following table, as prepared in the colonial laboratory, were dried in the sun in shallow trays, to which they had previously been transferred in the wet state. When sun dried, the masses were broken down, and the starches freely exposed to the air in the shade for ten days. Any adherent masses were then rubbed to powder by light pressure in a glazed mortar, and the whole sifted. Portions of each of these starches, and of others for the sake of comparison, were then dried, at 212 degrees Fahrenheit, in a current of dry air, and the loss determined:—