RUDIMENTS OF THE NATURAL SYSTEM OF BOTANY. 
259 
reference to the seeds ; no subsequent development ever disturbing their radical 
situation. Beyond that, however, the variations in their cuticle, technically termed 
the testa, are ofttimes noted with advantage. Their texture, too, is occasionally 
rendered subservient to the purpose of description ; and where they take any 
singular shape, such as that currently called winged, in which the sides of the 
testa are dilated and flattened, this is rarely disregarded. 
A minute scrutiny into the internal structure of most seeds — in the larger 
ones by the naked eye, and the smaller sorts with the aid of an adequate 
magnifying power — -will exhibit one or more cotyledons, the existence or non- 
existence of albumen, and the embryo of future vegetation. The cotyledons, 
or those comparatively large and thick plates of nutri mental matter which support 
the plant in its infant state, and are familiar to gardeners by the appellation of 
seed-leaves after germination has begun, are among the most valuable indications 
of affinity on an extensive scale. Although monocotyledons are, however, 
generally thought to be defined by the possession of one cotyledon, a much better 
mode of distinguishing them is by the position of their seed-lobes. In monoco- 
tyledonous plants, where there is more than one cotyledon, (which is not commonly 
the case,) they are arranged alternately ; and in dicotyledons they are uniformly 
opposite each other. 
Albumen, when present, is a nutritive substance, of various degrees of hardness, 
immediately surrounding the embryo, and always to be known from the cotyledons, 
by being separable from them, and having a connexion with the more directly 
vegetative organs. There are Orders in which, from its great dimensions, it forms 
an excellent feature for recognition ; but in some it is so imperceptible as to present 
no available difference. Its texture, which is diversified from soft and succulent to 
hard and horny in different Orders, must often be carefully noticed. 
Situated ordinarily at one end of the seed, and projecting itself therefrom when 
subjected to proper stimulants, the little embryo may be easily detected. It 
contains the rudiments of the young plant, which, on their primary development, 
extrude themselves in certain directions, these being peculiar in many Orders. 
The part that is afterwards to form the stem (or, in stemless plants, the leaves and 
axis) is the plumule ; while the little rootlet, which is alike the basis of subsequent 
subterraneous enlargements, receives the title of radicle. 
Having been largely indebted to the luminous explication of Dr. Lindley 
throughout the present series, we cannot finish it better than in the inferences he 
draws, that " No one can be at a loss to understand that to define any group oi 
plants, of what rank soever, is impracticable ; that differences of structure are of 
uncertain and unequal value ; and that the affinities of plants are never to be 
absolutely made out by solitary characters, but depend upon more or less intricate 
combinations, the power of judging of which is the same test of a skilful botanist, 
as an appreciation of symptoms is that of a physician." 
