ELEIVIENTARY ORGANS OF VEGETABLE TISSUES. 101 



greater number of vegetables, however, there is no germination until after th( 

 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 vegetate, varies from 

 one day to some years. The seeds of grasses and the grain-like plants, as rye, 

 wheat, corn, &c., 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* 

 Bays, 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 improvement in the knowledge of the animal economy ; and deficient in 

 the power of analogical reasoning must be that mind which is not, by the consider- 

 ation 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 

 fornied 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, fike 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 end« 

 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 plainly 

 to be seen in tlie node of the axis 

 * B. Barton. 



vi'^^^iv^"*'''^'^ °^ seeds— c. Language of vegetable physiology borrowed from animal physiology. 

 -115. Different aspects of vegetables to the careles:^ observer and the pliilosoplier— JiTicult to deter 

 mine where vegetable life commences. 



