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which vegetables are constructed, or to the external appearance their elementary organs assume in a state of combination. It is exceedingly desirable that these topics should be well understood, because they form the basis of all other parts of the science. In physiology, every function is executed through the agency of the organs : systematic arrangements depend upon characters arising out of their consideration ; and descriptive Botany can have no logical precision until the principles of Organography are exactly settled. A difference of opinion exists among the most distinguished botanists, upon some points connected with this subject, so that it has been found expedient to enter occasionally into much detail, for the purpose of satisfying the student of the accuracy of the facts and reasonings upon which he is expected to rely.

To this succeeds VEGETABLE PhysioLOGY (Book II.); or the History of the vital phenomena that have been observed both in plants in general, and in particular species, and also in each of their organs taken separately. It is that part of the science which has the most direct bearing upon practical objects. Its laws, however, are either unintelligible, or susceptible of no exact appreciation, without a previous acquaintance with the more important details of Organography. Much of the subject is at present involved in doubt, and the accuracy of some of the conclusions of physiologists is inferred rather than demonstrated; so that it has been found essential that the grounds of the more popularly received opinions, whether admitted as true or rejected as erroneous, should be given at length.

Next follows GlossoLOGY (Book III.); or, as it was formerly called, TERMINOLOGY; restricted to the definition of the adjective terms, which are either used exclusively in Botany, or which are employed in that science in some particular and unusual sense. The key to this book, and also to the substantive terms explained in Organography, will be found in a copious index at the end of the volume.

These topics exhaust the science considered only with reference to first principles; there is, however, another which it has been thought advisable to append, on account of its practical value, namely PHYTOGRAPHY (Book IV.); or, an exposition of the rules to be observed in describing and naming plants. As the great object of descriptions in natural history, is to enable every person to recognise a known species, after its station has been discovered by classification, and also to put those who have not had the opportunity of examining a plant themselves into possession of all the facts necessary to acquire a just notion of its structure and affinities; it is indispensable that the principles of making descriptions should be clearly understood, both to prevent their being too general to answer the intended purpose, or more prolix than is really requisite. It is the want of a knowledge of these rules that renders the short descriptions of the classical writers of antiquity, and the longer ones of many a modern traveller, equally vague and unintelligible. In this place are inserted a few notes upon the formation of an herbarium.

It has been my wish to bring every subject that I have introduced down, as nearly as possible, to the state in which it is found at the present day. In doing so, I have added so very considerable a quantity of new matter, especially in what relates to Vegetable Anatomy and Physiology, that the present edition may be considered, in those respects, a new work.

In the statements I have made, it has been my wish to render due credit to all persons for the discoveries by which they may severally have contributed to the advancement of the science; and if I have on any occasion either omitted to do so, or assumed to myself observations which belong to others, it has been unknowingly or inadvertently. It is, however, impracticable, and if practicable it would not be worth while, to remember upon all occasions from what particular sources information may have been derived. Discoveries, when once communicated to the world, become public property : they are thrown into the common stock for mutual benefit; and it is only in the case of debatable opinions, or of any recent and unconfirmed observations, that it really interests the world that authorities should be quoted at all. In the language of a highly valued friend, when writing upon another subject, — “ The advanced state of a science is but the accumulation of the discoveries and inventions of many: to refer each of these to its author is the business of the history of science, but does not belong to a work which professes merely to give an account of the science as it is : all that is generally acknowledged must pass current from author to author.” *

London, May, 1839.

* Brett’s Principles of Astronomy, p. v.

CONTENTS.

79

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Axis

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Hydrocyanic Acid

- 388
Chap. XIII. Circulation

389
Perspiration -

389
Rotation - - 391
Cyclosis -

393
Course of Sap . 400
Circulating Vessels • 401
Cause of Motion

• 402
CHAP. XIV. Directions

- 406
Chap. XV. Irritability . 418
Poisons .

. 419
Chap. XVI. Colour • 427
Chlorophyll

- 429
Xanthic and Cyanic Series - 432

Marquart's Views - . 434
CHAP. XVII. Odours

- 438

. 481

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