ELEISIENTAEY ORGANS OF VEGETABLE TISSUES. 
101 
greater number of vegetables, however, there is no germination until after the 
opening of the pericarp and the fall of the seed. The time at which different 
species of seeds, after being committed to the earth, begin to vegetatp^ varies from 
one day to some years. The seeds of grasses and the grain-like plants, as rye, 
wheat, corn, (fee, germinate within two days. The cruciform and the leguminous 
plants, as the pea and bean, require a little more time. The peach, walnut, and 
peony, remain in the earth a year before they vegetate. All kinds of plants germi- 
nate sooner if sown immediately after being separated from their pericarps. Many 
vegetables preserve their vital principle for years ; some lose it as soon as they are 
detached from their pericarps ; this is said to be the case with respect to coffee 
and tea. It is asserted that mosses, kept for near two hundred years in the herba- 
riums of botanists, have revived by being soaked in water. An American writer* 
says, that " seeds, if imbedded in stone or dry earth, and removed from the influ- 
ence of air or moisture, might be made to retain their vegetative quality or principle 
of life for a thousand years — and he adds, " life is a property which we do not 
understand ; yet life, however feeble and obscure, is always life, and between it 
and death there is a distance as great as existence and non-existence." 
c. The subject of vegetable physiology, though highly interesting, is in many of 
its details too complicated for the youthful investigator ; but enough has now been 
presented to show how large a field this science covers. The physician finds in the 
vegetable organization striking analogies to the internal structure of the animal 
frame ; to him the language of physiological botany is familiar, because it is bor- 
rowed from his own science. On the other hand, the botanical student, in learning 
the names and offices of the various internal organs of plants, is making no incon- 
siderable im[»rovement in the knowledge of the animal economy ; and deficient h\ 
the power of analogical reasoning must be that mind whicli is not, by the consider 
atioa of the one, led to reflect upon the organization of the other. 
LECTUEE XIX. 
PHYSIOLOGICAL VIEWS. ELEMENTARY ORGANS OR VEGETABLE TIS 
SUES. SOLID AND FLUID PARTS OF VEGETABLES. 
115. The careless observer of nature may consider the trunk of a tree, a leaf, or 
A stem of an herb, as very simple in its structure, presenting little more than a 
homogeneous mass; but the botanist has learned that plants, like animals, are 
formed of tissues of different kinds, variously fitted to carry on the operations of 
imbibing nourishment, of making a chemical analysis of the same, of appropriating 
to themselves such elements as are necessary to promote their health and vigor, 
and of rejecting such as are useless ; — in short, that they have parts which are anal- 
ogous to skin, bones, flesh, and blood : that they are living, organized beings, com- 
posed of solid and fluid parts ; and, hke animals, are the subjects of fife and death 
Plants differ from animals in being destitute of the organs of sense. They can 
neither see, hear, taste, smell, nor touch. Some vegetables, however, seem to have 
a kind of sensibility like that derived from the organs of touch ; they tremble and 
shrink back upon coming in contact with other substances ; some turn themselves 
round to the sun as if enjoying its rays. There is a mystery in these phenomena. 
It is not yet fully known at what point in the scale of existence animal life endu 
and vegetable life commences. Some beings, like the sponge and corals, seem 
in a germinating state ; the radicle was like a little beak ; the tuft of leaves and the stem were plainlj 
to be seen in the node of the axis, 
* B. Barton. 
Vital principle of seeds — c. Language of vegetable physiology borrowed from animal physiologj 
-115. Different aspects of vegetables to the careless observer and the philosopher — Jifficult to deter 
wine w/iere vegetable life conunences. 
