ts who in comparatively recent years have monographed the
group, Parlatore (_Le Specie dei cotoni_, 1866) recognizes seven
species, whilst Todaro (_Relazione sulla culta dei cotoni_, 1877-1878)
describes over fifty species: many of these, however, are of but little
economic importance, and, in spite of the difficulties mentioned above,
it is possible for practical purposes to divide the commercially
important plants into five species, placing these in two groups
according to the character of the hairs borne on the seeds. Sir G.
Watt's exhaustive work on _Wild and Cultivated Cotton Plants of the
World_ (1907) is the latest authority on the subject; and his views on
some debated points have been incorporated in the following account.

[Illustration: From Strasburger's _Lehrbuch der Botanik_, by permission
of Gustav Fischer.

FIG. 1.--Seed-hairs of the Cotton, _Gossypium herbaceum_. A, Part of
seed-coat with hairs; B_1, insertion and lower part; B_2, middle part;
and B_3, upper part of a hair.]

A seed of "Sea Island cotton" is covered with long hairs only, which are
readily pulled off, leaving the comparatively small black seed quite
clean or with only a slight fuzz at the end, whereas a seed of "Upland"
or ordinary American cotton bears both long and short hairs; the former
are fairly easily detached (less easily, however, than in Sea Island
cotton), whilst the latter adhere very firmly, so that when the long
hairs are pulled off the seed remains completely covered with a short
fuzz. This is also the case with the ordinary Indian and African
cottons. There remains one other important group, the so-called "kidney"
cottons in which there are only long hairs, and the seed easily comes
away clean as with "Sea Island," but, instead of each seed being
separate, the whole group in each of the three compartments of the
capsule is firmly united together in a more or less kidney-shaped mass.
Starting with this as the basis of classification, we can construct the
following key, the remaining principal points of difference being
indicated in their proper places:--

i. Seeds covered with long hairs only, flowers yellow, turning to red.

A. Seeds separate.
Country of origin, Tropical America--(1) _G. barbadense_, L.
B. Seeds of each loculus united.
Country of origin, S. America--(2) _G. brasiliense_, Macf.

ii. Seeds covered with long and short hairs.

A. Flowers yellow or white, t