639 



BOTANY. 



tions, to say nothing of the extensive gardens where 

 plants are raised for sale. In France, the royal gar- 

 den in Paris, under the inspection of Dest'onUiines 

 and Thouin, is the principal. Formerly that of Mal- 

 inaison, founded by the empress Josephine, was the 

 most famous. In Italy, the garden of the university 

 at Turin, superintended by Capelli, is. perhaps, the 

 best ; in Spain, the royal garden at Madrid, under 

 Mariano Laga*cu; in Denmark, the garden of the 

 university at Copenhagen, under the superintendence 

 of Homemann. In Russia, the excellent institution 

 of the count Alexis Uasumowsky, at Corinka, near 

 Moscow, deserves to be placed by the side of the most 

 celebrated establishments. The principal botanical 

 gardens in America arc in New York, Philadelphia, 

 and Cambridge. In Asia, the garden of the East 

 India company at Calcutta is the most important 

 At present, nlmost all universities and learned aca- 

 demies, as well as many rich private proprietors, have 

 botanical gardens. 

 BOTANY, the science of plants,* may be divided into 



two parts, one of which describes their external ap- 

 earance, and is sometimes called phytography ; the 

 ther treats of their internal structure and organic 

 ction, and may be termed philosophical botany or 

 Autonomy. The former requires a perfect know- 

 ?dge of terminology, the latter a thorough know- 

 *dge of the plants themselves, with a view to a sys- 

 emutic classification of them, according to fixed 

 rinciples. The necessity of such a classification 



must have been felt as soon as the number of known 

 Lint-, became great, and their relations and analo- 

 gies obvious. At the time of the revival of letters, 

 ardly 1500 plants were known from the descriptions 

 f the ancients. At present, at a moderate estimation, 

 early 100,000 have been described. It is obvi- 

 usly impossible to introduce order into this Infinite 

 haos, or to acquire any distinct knowledge, without 

 lie aid of general principles. Even in the sixteenth 

 nd seventeenth centuri.es, the founders of botanical 



science perceived that in plants, as well as in all 

 >ther natural bodies, the essential and necessary 



Plant* are generally defined as being organized bodies 

 without Toluntary motion. In this case, however, as in 

 numberless others, it ii much easier to understand the 

 word than to find a definition sufficiently comprehensive 

 and sufficiently exclusive. Plants consist, like all organ, 

 ixed bodies, of solid and fluid parts. To the former belong 

 the cellular substance, the various vessels, the fibres, and 

 the pith (see Medulla) ; to the latter belong the sap and 

 the various juices, as well as the air contained in plants. 

 The air, the sap, and the juices, have appropriate vessels. 

 The entire or proper vessels, so called, are intended to 

 contain the proper juices of the plant, and are generally 

 found filled with oils or resinous juices. They are generally 

 in bundles in the cellular part of the bark, and are found 

 in the young shoots of almost every plant. The spiral ves- 

 sels, to called from their appearance, are the largest of the 

 vegetable vessels, and in many plants their structure is 

 visible to the naked eye. Their nature and their real 

 economy are very obscure. They are situated round the 

 medulla of the young shoots of trees and shrubs. The vef. 

 forated vessels are cylindrical tubes, the sides of which 

 are said to be pierced with minute perforations. They 

 have, apparently, no office but that of air vessels. The 

 fluid substances of plants move in the vessels just enumer- 

 ated. The proper juices contain nourishment adapted for 

 assimilation into the substance of the plant. They corre- 

 spond in plants to what we call in animals blood, and may 

 well be compared with it as to their functions. In a phy- 

 siological respect, many points of correspondence between 

 animals and plants are observable. Power of contraction, 

 irritability, power of formation, power of reproduction, and 

 other powers, are possessed by plants as well as by ani- 

 mals, though in a lower degree. The vital power preserves 

 in plants, as it does in animal bodies, in all the changes to 

 which they are subject, the peculiar character of the indi- 

 vidual; and by it the chemical affinity of the primitive 

 substances of which organic bodies consist is modified, so 

 as to be different from what it is in inorganic bodies. Ii 

 this vital power ceases, the organic body dies, and its com- 

 ponent parts become subject immediately to the universal 

 laws of affinity prevailing in inanimate nature. Whether 

 sensation is to be ascribed to plants is doubtful, because, as 

 yet, no nerves have been discovered in them ; and the 

 phenomena connected with certain plants, which seem to 

 indicate the existence of sensation in them, may, perhaps 

 be reduced to simple irritability. Motion, as a consequence, 

 f vital power, is not to be denied to plants. Several p 

 them, under certain circumstances, exhibit a motion in 

 certain external parts, which is similar to that of animals 

 The motion of the juices in plants was known long before 

 its causes was understood. Malpighi seems to have lookec 

 for the cause in a movement of the vessels ; Hales in the 

 warmth of the atmosphere ; later naturalists have referrei 

 it to mechanical causes, considering the vessels of plants a 

 capillary tubes (q. v.). But the insufficiency of these ex 

 planations is easily seen, and it appears more correct to 

 consider the irritability of the vessels as the cause of the 

 rising 1 ot their juices. This view is confirmed by the fac 

 that the juice ceases to rise if the irritability of the vessel 

 is deadened by electric shocks. But in what this irritabili- 

 ty consists, and how it operates, has not, as yet, been de 

 monstrated. Only its existence is known ; and experimenti 

 have proved that, by certain artificial means, it may b 

 increased as well as diminished, nay, entirely destroye< 

 Warmth, moreover, seems to influence the motion of th 

 juices in plants ; otherwise why should not the irritabilit 

 produce motion in the juices in winter 7 A certain degre 

 of heat ii necessary before the juices begin to rise and th 



rowth to proceed. Cold weather immediately produces a 



heck or suspension. The heat of summer appears to 



weaken this irritability by degrees, till at length the juices 



move more and more slowly, and begin to stand still in 



autumn. With the irritability of plants, too, their sleep 



ind their turning towards the light are closely connected. 



'he former seems to ensue after they have been in con- 



inued and violent activity. It is particularly observai.U: 



n the corolla, but also, in a lower degree, in the leaves. 



'he. disposition of plants to turn towards the light is easily 



seen in such as have light from one side only, as all the 



stalks, branches, leaves, and blossoms, turn in that direc- 



ion. 



Another important point in the physiology of plants is 

 heir breathing. This consists in an absorption and exha. 

 ation, especially observed in the case of the leaves. If a 

 resh leaf is put in a tumbler filled with spring- water, and 

 exposed to the rays of the sun, it soon appears covered 

 with small air-bubbles, which by degrees rise to the sur- 

 ace of the water, where they burst. If they are caught, it 

 s found that they contain oxygen. The light of the sun is 

 necessary to this phenomenon ; 'mere heat is insufficient to 

 produce it. Experiments respecting tk<*. breathing of 

 slants have led to very different opinion*. Ingenhouss 

 Links that plants exhale oxygen only in the light of the 

 sun, but during the night azote and carbonic acid gas. 

 According to Senebier, healthy plants and their leaves do 

 not exhale any air whatever during the night ; the same 

 was maintained by Spallanzani. Ackermann, on the other 

 band, maintains that plants, like animals, must continually 

 inhale the basis of vital air (oxygen), and exhale carbonic 

 acid. But plants exhale not only gaseous matter ; fluids 

 are evaporated from them, the amount of which is con. 

 siderable. It is asserted that a tree of middling size eva- 

 porates daily about thirty pounds of moisture. 



As to the odour of plants, the recent progress of cheinis. 

 try shows that the basis of it does not (as might have been 

 supposed of so fleeting, diffusible, almost imponderable, 

 entirely invisible a substance, affecting only the olfactory 

 nerves) consist of a gaseous matter. Fourcroy showed that 

 there does not exist a separate principle of scent. This 

 property is as essential to bodies ad gravity, but is proper 

 tionate to their volatility : the most volatile bodies have the 

 strongest odour. 



The taste of plants seems to depend on the proportion? 

 of their elementary ingredients, and on the degree of heat 

 to which the plant is exposed. The rays of the sun, also, 

 have a powerful influence on it. 



Of the colours of plants, the same is true that has been 

 said of their scent. Even Aristotle observed that plants 

 are coloured by the sun. Ray, Bonnet, Senebier, and 

 others, made various experiments connected with this 

 point. Senebier found that when plants were put in a 

 dark place, their green leaves become first yellow on the 

 surface and then white ; whilst young plants which had 

 grown up in the dark, when brought by him gradually to 

 the light, exchanged their white colour for yellow, which, 

 after a while, became darker, and showed by degrees green 

 spots, continually increasing in number and size, so that, 

 after some time, the parts before white acquired a perfectly 

 green colour. With blossoms raised in the dark the change 

 of colour is but slight Bonnet asserts the co-operation of 

 heat in this process ; but, according to the experiments of 

 Van Mons and Vasalli, the light of lamps and of the moon 

 operates in the same way. The cause of this remarkable 

 phenomenon seems to be, that plants beconTe lighter 

 in consequence of combination with the oxygen which 

 they inhale, darker if they lose it. The different propor- 



