AND THE STRUCTURE OF PLANTS. <J5 



volatile nymph ammonia, which is an invisible gas, the fruit of their embraces 

 will be still more extraordinary in point of form, for the gas and the liquid 

 will engender that solid substance commonly known by the name of sal am- 

 moniac, or, in the new nomenclature, muriate of ammonia. In like manner, 

 our common smelling salts, or carbonate of ammonia, though a hard, concrete 

 crystallization, are the mere result of the union of two invisible gases, am- 

 monia and carbonic acid gas, or fixed air ; and which, having duly paid their 

 court to each other, give birth to this solid substance. 



But in ail this it may be said that we have no instance of a multiplication 

 of species ; nor in reality of any thing more than the production of a third 

 substance, issuing, like the fabled phoenix of antiquity, out of the ashes or 

 decomposition of the parent stock ; yet in many cases we have instances 

 of multiplication also and instances far more extraordinary and far more 

 prolific than are ever to be found in the multiplication of either animals or 

 vegetables. Such especially are those wonderful increases that occur in the 

 case of ferments and of contagions. A few particles of yest lying dormant 

 in a dessert-spoon are introduced into a barrel of beer, or of any other fer- 

 mentable fluid, and in a few hours propagate their kind through the largest 

 vessel that was ever manufactured ; so that at length every particle of the 

 fluid is converted into a substance of their own nature. A few pestilential 

 miasms are thrown forth from a stagnant marsh or a foul prison, and give 

 birth instantaneously to myriads and myriads of the same species of particles, 

 till the atmosphere becomes impregnated with them through a range of many- 

 miles in diameter. Two or three particles of the matter of plague are packed 

 up in a bag of cotton at Aleppo, and are many months afterward set at liberty 

 in Great Britain. Aided by the stimulus of the air, they instantly set to 

 work, and procreate so rapidly, that the whole country in less than a week 

 is laid prostrate by the enormity of their increase. 



Now the terms loves and marriages will just as well apply to all these as 

 to the vegetable creation. The cause of the respective unions, and of the 

 changes that take place in consequence of such unions, are in both cases 

 nothing more than elective attractions : in the mineral and gaseous kingdoms 

 produced by what chemists have denominated the principle of affinity, and in 

 the vegetable by what physiologists have called the principle of irritability; 

 a principle far nicer and nobler and more delicate than that of affinity, and 

 under the influence of an internal, an all-pervading, and identifying vital 

 power, capable, as differently excited by different stimulants, of producing 

 far nicer and nobler, more delicate and more complicated effects ; but which 

 in itself is not more different from the principle of affinity i\m\\ it is from that' 

 of sensation. 



No experiment or observation has hitherto proved vegetables to be pos- 

 sessed of any higher powers than those of irritability, contractility, and 

 those instinctive energies which we shall hereafter show are dependent upon 

 the principle of life. 



It is almost superfluous to observe, in this place, that there are also powers 

 and faculties of a much higher character than any I have yet noticed, apper- 

 taining to the nobler ranks of animals; for at present I am only pointing out 

 the leading characters by which animals in general may be distinguished 

 from vegetables in general, and shall have sufficient opportunities, as we pro- 

 ceed, of adverting to these additional faculties, and of investigating their 

 respective excellencies. 



Our immediate concern, then, is with VEGETABLE LIFE ; its general laws, 

 structure, and phenomena. And upon this subject I shall touch as briefly as 

 possible, intending it as a mere vestibule or introduction to the more impor 

 tant study of animal philosophy. 



Plants, then, like animals, as I have already observed, are produced by 

 generation, and through the medium of ova, or eggs. The exceptions to this 

 common rule are few, and they occur equally in both kingdoms. The egg 

 of the plant is its seed ; a doctrine not of modern origin, but taught and un- 

 derstood quite as clearly, and with as close a reference to the rise of animal 



