STRUCTURE OF THE SEED—THE INTEGUMENTS., 330 
1. THe INTEGUMENTS OR Coats.—There are two seed-coats 
orinteguments. These have been variously named by botanists ; 
the terms employed in this volume, and those most frequently 
used, are testa or episperm for the outer coat; and tegmen or 
endoplewra for the inner. 
a. Testa, Episperm, or Outer Coat (fig. 748, te).—This integu- 
ment may be either formed of the primine of the ovule only, or, 
as is more frequently the case, by the combined primine and 
secundine. The testa is generally composed of ordinary paren- 
chymatous cells ; but in some seeds, as in those of Acanthodiwm, 
we have in addition a coating of hair-like cells containing spiral 
fibres (see page 65). These cells are pressed closely to the 
surface of the seed by a layer of mucilage ; hence if such seeds 
be moistened with water, the mucilage which confines them 
becomes dissolved, by which they are set free, and then branch 
out in every direction. It frequently happens, also, that the 
membrane of the cells is ruptured, and the elastic fibres which 
they contain then becoming uncoiled, extend to a considerable 
distance from the testa. The seeds of Collomia (see page 45) 
and many other Polemoniaceous plants, &c., exhibit this curious 
structure, and form beautiful microscopic objects. 
Colour, Texture, and Surface of the Testa.—In colour, the 
testa is more generally of a brown or somewhat similar hue, as 
in the Almond, but it frequently assumes other colours ; thus, 
in some Poppies it is whitish or yellowish, in others black, 
in Indian Shot (Canna) and Peony also somewhat black, in 
the Arnatto and Barricarri (Adenanthera) red, in French Beans 
and the seeds of the Castor-oil plant beautifully mottled, 
and various other tints may be observed in the seedsof different 
lants. 
a The testa also varies in texture, being either of a soft nature, 
or fleshy and succulent, or more or less spongy, or membranous, 
or coriaceous, or when the interior of its cell-walls is much thick- 
ened, it assumes various degrees of hardness, and may become 
woody, crustaceous, Xe. 
The surface of the testa also presents various appearances, 
and is often furnished with different appendages. Thus it may 
be smooth, as in Adenanthera ; or wrinkled, as in Nigella ; 
striated, as in Tobacco ; marked with ridges and furrows, as in 
Delphinium (fig. 751); netted, as in Nasturtium (fig. 749) ; 
alveolate or pitted, as in the Poppy (jig. 750) ; tuberculated, as 
in Chickweed (fig. 752) ; spiny, as in the Mulberry, &. The 
testa of some seeds is also furnished with hairs, which may 
either cover the entire surface, as in the various species of 
Gossypium where they constitute the material of so much value 
called Cotton (see page 67), and in the Silk-cotton tree (Bom- 
bax); or they may be confined to certain points of the surface, 
as in the Willow (fig. 756), Asclepias (fig. 755), and Epilobium 
(fig. 761). In the latter cases the tufts of hairs, thus contined to 
