8 
erality observable in the reproductive organs, the flower and fruit. 
The seeds of Exogene have a structure which may be illustrated by 
the Bean, Lupine, Radish, &c. Upon removing the outer coats of the 
seed we find the Embryo or young plant, composed of two fleshy lobes 
attached to a conical mass, which latter elongates and becomes 
the root. These lobes, figure 5, are termed cotyledons, and in 
some plants, as the Pea, they remain underground during the rig. s. 
process of germination, whilst in others, as the Lupine and Radish, they 
rise above ground, and as a green ting 
true leaves. They are leaves of the embryo, des- 
tined to afford it nourishn est stages of its development. 
These cotyledons are so vided into two parts, so that we 
occasionally find three or f which generally have only two, 
and this shews us on between these exogenous 
al e of the fir tribe ere) which have several coty- 
ledons forming a whorl round the stem: figure 6. _ The term 
Dicotyledones (from dug TWICE, xorv\qoy KOTYLEDON, a seed-lobe) 
has been also given to the Class Exogene, hecause the great ma- Fig, 6. 
jority of its species have two cotyledons to their embryo; and though, 
as we have stated, there are a few cases where the cotyledons are more 
than two, yet in these: they are always ranged round the stem in the 
same horizontal plane, and are not placed one above another. 
A singular exception to the Dicotyledonous structure of an Exogen- 
ous plant occurs in the genus Cuscuta whose embryos have no cotyle- 
dons; but as the leaves of these plants are always abortive, and there 
are scarcely any traces of them left, it is reasonable to consider their 
cotyledons also to be abortive rather than to suppose them essentially 
wanting. 
In the seeds of Endogenz there is but one cotyledon, which in 
germination grows in the form of a fleshy cone, and then (figure 
7) the leaves rise up in succession and expand one within the 4.7. 
other at different heights along the stem, as in the Grasses, 
figure 8, Hence the name of Monocotyledones, (povoe Monos, 
alone, corvAndoy KoTyLEDON, a seed-lobe) been given to this 25. 
ass. The embryo is frequently very minute, and its parts not easily 
distinguishable before germination. commences. ‘ 
