OUTLINE OF STRUCTURAL BOTANY 41 
class may have more than one cotyledon, while exceptions, like the 
seed of the African Kola tree, in which there may be from one to 
several cotyledons, occasionally occur in the other class. 
These cotyledons with the enveloping tegument and the embryo 
comprise the essential elements of the seed. 
Commencing our examination with the tegument we find that 
not only does it invest the seed, but that while apparently a single 
organ it consists, in fact, of several layers of each to which names 
are given,1 
To the outer membrane or layer which is commonly smooth, as 
we see it on the grain of corn or wheat, may occur various modifica- 
tions which are devices for the dissemination or protection of the 
seeds. These modifications may be in the form of appendages such 
as hairs, hooks, bristles or wings. 
The ovule is held in relation to the ovary by a little connective 
organ, the funiculus, and the point at which this little pene of 
union is attached to the ovule or seed is marked, 
when the latter separates from the ovary, by a spot 
known as the chalaza. 
The essential part of the seed is, of course, the 
embryo, which is, in fact, the rudimentary young 
plant, and it is to this that all other parts of the 
seed are subsidiary. ‘Thus, the cotyledons store up 
nutriment which will be required by the embryo 
during the early stages of its development until it 
can draw its nourishment from the soil or other 
environment. 
The embryo consists of a radicle which is des- 
tined to form the root and of a plumule, the rudi- 
ment of the stem and leaves (Fig. 67). The coty- 
ledons occupy, as a rule, much the largest portion 
of the seed and form, in dicotyledonous plants, the 
first pair of leaves which are often thick and fleshy fre. 67— Gaty: 
(Figs. 67 and 68), while the single cotyledon of the agp cease 
grain of corn forms, in germination (Fig. 70) a bryo between, 
storage body which does not rise above the surface 
of the soil and does not assume a green color, as do the cotyledons 
of the bean, the maple or the oak. 
While the nutrient material is often stored in the cotyledons, a 
reservoir of nutritious matter is sometimes found in an independent 
body known as the albumen, which varies in its nature and position. 
+The outer layer of the integument is the testa, the second is the mesosperm and 
the third the endosperm, 
