16.  Sweet Cassava (Janipha Loeflingii).—­Grown on No. 1 Canal, Demerara River.

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.
------------------+-------+-------+-------------------------

----------------
|       |Tem. at|
Names of     |Density|time of|               Remarks
Plants      |       |Obs.  F.|
------------------+-------+-------+-------------------------

-----------
1.  Bitter cassava|1.4  3 | 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