100 BOTANY FOR BEGINNERS. {Ch. XV1 
the moisture proceeds; while some imagine that the plant is en- 
dowed with a kind of instinct, similar to that which appears in 
animals, leading the little duck to seek the water, and birds to 
attempt to fly; but let us call this power by what name we 
will, or refer it to whatever secondary laws, we must after all 
attribute it to the will and design of Him, who gave the plant 
a principle of life. 
415. After the young root has made some progress, the coty- 
ledons swell, and rising out of the ground, form two green leaves, 
called seed leaves. You have no doubt noticed their appear- 
ance in the garden bean, when it first appears above the ground. 
416. When the plume develops its leaves, these seed-leaves, 
being no longer needed, wither and decay. 
417. You will recollect that the embryo or germ is composed 
of two parts, the radicle and the plume. The radicle, we have 
Just seen, extends itself downwards. Soon after this part of 
the germ has begun its downward course, the plume, (so called 
from its resembling a little feather,) rises upwards, and soon 
becomes a tuft of young leaves, with which the stem, if there 
is one, ascends. 
418. Some moisture is essential to. the germination of the 
seed, though different plants require different quantities. Wa- 
ter softens the envelopes of the seed, swells the kernel, and 
causes it to burst. ‘Too much water produces a decay or rot in 
the seed so rapidly, that the living principle is destroyed rather 
than brought forward ; hence it is better to sow seeds in dry ra- 
ther than wet weather. arth, though not absolutely essential, 
is useful, as affording to the vegetable egg a favourable situa- 
tion, where it may receive the influence of the various agents. 
which are to perform their offices in the development of its 
parts. Some plants vegetate without earth. The parasite grows 
upon the barks of other plants; many seeds vegetate in water, 
and some, when moistened and placed on cotton, or any other 
supporting substance. 
419. Airis essential to vegetation ; under an exhausted recei- 
ver aseed will not germinate, although possessing every other 
requisite. Seeds that become imbedded deeply in the ground 
do not vegetate, unless accidentally ploughed up, or exposed to 
the atmosphere. Acorns, supposed to have lain for centuries, 
have germinated as soon as they were raised sufficiently near 
the surface to receive the influence of air. You will recollect, 
415. When do the seed leaves appear ? 
416. When do the seed leaves decay ? 
417. What direction does the plume take? 
418. What effect has water upon the vegetation of the seed 2—Is 
earth essential to vegetation ? 
419, {s air necessary te vegetation ? 
