OUTLINES OF BOTANY. 
XXXV 
evolution of its parts; it accordingly possesses, in a rudimentary state, all 
the essential organs of vegetation, as has already been shown (12-17). 
The preexisting first joint (internode) of the axis is the Radicle, and the 
seed-leaves it bears are the Cotyledons. 
219. The embryo of Endogenous Plants (p. 445) bears a single cotyledon 
(or only one seed-leaf on its primary node, 13), or is monocotyledonous. 
That of Exogenous Plants (p. 1) bears two opposite cotyledons, and is 
therefore dicotyledonous , or rarely 3 or more in a whorl ( polycotytedonous ), 
as in Pines (p. 439). 
220. In large embryos, the rudiment of the second node, with its leaf or 
leaves, is sometimes apparent or more or less conspicuous anterior to ger¬ 
mination : this growing apex, or bud, is named the Plumule. 
221. Whatever be the form and nature of the seed, the radicle lies adja¬ 
cent to its organic apex, or micropyle (179), towards which the root-end 
(the extremity opposite to the cotyledons) invariably points. It is accord¬ 
ingly next the hilum in anatropous seeds, but remote from it, at the oppo¬ 
site end, in orthotropous seeds. Considered with respect to the pericarp, 
the radicle is superior when it is directed towards the apex of the fruit; 
in/enor when it points towards its base, &c. 
222 The germination, or development of the embryo from the seed, 
and its establishment as an independent individual plant, completes the 
cycle of vegetable life, and brings us round to the point at which this 
account began. 
223. The conditions requisite to germination are a certain amount of 
heat (according to the nature of the species), moisture, darkness, and a 
free communication with the air. Seeds are in the most favorable condi¬ 
tion for germination, therefore, when loosely covered with soil, which ex¬ 
cludes the light while it freely admits the air, and is moistened by showers 
and warmed by the rays of the sun. The water which is slowly absorbed 
softens all the parts of the seed, and serves to dissolve the starch and 
other nutritive matter contained in the cotyledons or accumulated in the 
surrounding albumen (a portion of which is decomposed and converted 
into carbonic acid and water with the evolution of heat, while the remain¬ 
der is usually brought into the more soluble forms of dextrine, sugar. &c.); 
the enlarging embryo bursts its envelopes ; the radicle is protruded, and, 
taking a downward direction, fixes itself in the soil; while the budding end 
elongates in the opposite direction to elevate the plumule above the^ sur¬ 
face, when the leaves expand in the air and light (12-17). 
224. In most Exogens, the cotyledons are brought to the surface in ger¬ 
mination and expand in the air, as in the Maple, Beech, and Bean. But 
when greatly thickened and gorged with nourishing matter deposited in 
their tissue, they remain under ground (as in the Oak, Horsechestnut, 
Pea, &c.), the plumule alone rising above the surface, and its primordial 
leaves being the earliest to expand. So, likewise, the single cotyledon in 
Endogens always remains subterranean. 
225. In the Mangrove, &c., and also in some casual cases, the embryo 
germinates while the fruit is still attached to the parent stem ; or is, as’ it 
were, viviparous. 
11. Cryptogamous or Flowerless Plants. 
226. Cryptogamous Plants of the highest grade, such as Ferns, Horse¬ 
tails, and Club-mosses, do not essentially differ from Phsenogamous Plants 
(2) in anatomical structure and in their vegetation; except that their stems 
grow from the apex only, and have no particular provision for subsequent 
increase in diameter: hence they have been named Acrogens, or Point - 
growers (p. 618). 
227. Their organs of reproduction are so diverse in different families 
