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BOTANY. 



an observation of the uniformity of nature in the for- 

 maiioii of those parts in plants of similar kinds. But 

 it was found, also, that uniformity iu these formations 

 prevailed in too great a number of plants to allow 

 them alone to be made the distinguishing cliar.ici* n>- 

 tics. 1 1 became, therefore, necessary to have recourse 

 to other parts. The flower was lir-i. chosen, as it 

 presents a great variety of forms, and, at the same 

 time, a uniformity of structure. But the limits to 

 Hi is uniformity, and the absence of flowers in innu- 

 merable plants, with the consideration that they are 

 not essential, suggested to the immortal founder of 

 modern scientific botany the idea that the sexual 

 parts are most intimately related to the growth of the 

 Iruit, and that they are, therefore, of the greatest 

 importance, and furnish better grounds of classification 

 than the flower. A general principle was thus 

 established, fertile in consequences, excellently adapt- 

 ed to facilitate the diffusion and extend the sphere of 

 the science. The Linnoean system was founded 

 exclusively on the relations of the sexual parts. 

 Liruueus divided all known plants into two general 

 divisions, one of which has visible sexual parts (pha- 

 nerogamous), while in the other they are invisible 

 or wanting (cryptogamous). The first division com- 

 prehends the twenty-three first classes of his system, 

 which are distinguished according to the situation 

 of the sexual parts in the same or in separate 

 flowers, their number, their length, &c. If any sys- 

 tem has introduced order in the midst of variety, and 

 shed light on the immense diversities of nature, it is 

 that of Linnaeus. Hence, even those who have 

 departed from it in their writings have considered it 



the ferns upward, in the more perfect plants, surrounded 

 by the vessels in bundles and single. In the trunk of com. 

 mon trees, it generally forms the alburnum and the wood. 

 With the palms, the grasses, &c., the spiral bundles are 

 distributed in the cellular texture. The spiral canals pass 

 through all parts. Through the leaf-stalk, they penetrate 

 with the vessels that convey the juices into the nerves of 

 the leaves, through the flower stalk into the corollsp, into 

 the filaments, the ovaries, the pistils, even into the seeds. 

 As long as they remain original, they have no wall, but that 

 which is formed by those winding fibres. But they are not 

 always found in this original form. They appear often as 

 annular vessels, often as stair-shaped, or as perforated ves- 

 sels, &c. At length there are transitions from them to the 

 cellular form, particularly in the trees with acicular leaves- 

 Here appear oblong cells perforated with regular holes 

 provided with margins ; nay, in the yew we even find cells 

 with divisions winding spirally, which probably take the 

 place of the spiral canals not existing here. The function 

 of this third original formation seems to be the preparation 

 and conducting of the 'gases, the moisture, &c., which pro- 

 ceed from the juices of the plants. 



II. Particular Structure of the single Parts of Plants. 

 The root The surface even of the firmest roots is sur- 

 rounded with fine hairs, and the points are covered with a 

 spongy cap, by which and the hairs the absorption of the 

 moisture in the ground is carried on. A bundle of tubes 

 passes through the centre of the root, in which there is no 

 pith The stem consists in woody dicotyledonous plants of 

 three distinct parts the bark, the wood, and the pith. 

 The bark is composed of four parts, 1. a dry, leathery, 

 tough membrane, the cuticle ; 2. a cellular layer adhering 

 to the cuticle, and called the cellular integument; 3. a vas- 

 cular layer ; and, 4. a whitish layer, apparently of a fibrous 

 texture, the inner bark, which is of a more complicated 

 structure than the other layers. The wood is at first soft 

 and vascular, and is then called alburnum; but it after- 

 wards becomes hard, and in some trees of a density almost 

 approaching that of metal. It is composed of concentric and 

 divergent layers, the former consisting of longitudinal fibres 

 and of vessels of various kinds, the latter of flattened 

 masses of cellular substance, which cross the concentric 

 layers. The individual cells are narrow and horizontal in 

 their length, and extend in series from the centre to the 

 circumference of the wood, so as to form nearly right angles 

 with the tubes of the concentric layers. Various opinions 

 have been entertained respecting the origin of the wood or 

 alburnum. Mr Knight has proved that the alburnum is 

 formed from the secretion deposited by the vessels of the 

 liber. Wopd, while in the state of alburnum, is endowed 

 with nearly as much irritability as the liber, and performs 

 functions of great importance in the vegetable system ; but 

 when it is hardened, these functions cease, and in time it 



necessary for elementary instruction. Many objec- 

 tions, however, are brought against it. It has been 

 made a question whether it is fitted for the investiga- 

 tion and classification of unknown plants. It is said 

 that the sexual parts may be very different in similar 

 plants ; that he never will have a complete idea of 

 nature, who proceeds only on one principle. It has, 

 therefore, been thought necessary to find a more 

 natural arrangement. In order to follow nature, we 

 must look at every part ; at the internal structure, us 

 well as the external relations, analogies, and differ- 

 ences. This can be done only by a profound rind 

 toilsome investigation, of which the mere follower of 

 a system has hardly a notion. Seed is considered as 

 the ultimate object of vegetation. Its parts, their for- 

 mation, situation, and other relations, must be criti- 

 cally examined. The most perfect natural system, 

 in modern times, is that of Jussigu, particularly as 

 enlarged by -Decandolle. (See Decandolle's Regni 

 vegetabilis Systema naturale, his Theorie elementaire 

 de la Botanique, and his Prodromus Systematis natu- 

 rails Regni vegetabilis ; also the Kouveaux Element 

 de la Botanifite, by Richard) 



The second general division of this science begins 

 with the investigation of the internal structure, or the 

 anatomy of plants. This study has been recently 

 cultivated, by the Germans, to an extent, which, 

 thirty years ago, could hardly have been conceived. 

 It is closely connected with the first division, if the 

 plants are studied in their natural order. Without 

 good microscopes, and the aid of the best works in 

 this branch, a distinct knowledge of the structure of 

 plants cannot easily be obtained. Chemical botany 



loses its vitality, not unfrequently decaying in the centre 

 of the trunks of trees, which often, however, put out new 

 shoots, as if no such decay existed. To carry on, therefore, 

 the functions of the wood, a new circle is annually formed 

 over the old. The hardness of these zones increases with 

 the age of the tree, those in the centre being most dense. 

 In the centre of the wood is the pith, enclosed by the me- 

 dullary sheath. The pith or medulla in the succulent 

 state of a stem or twig, is turgid wth aqueous fluid, but, 

 before the wood is perfected, it becomes dry and spongy, 

 except near the terminal bud, or where branches are given 

 off, in which places it long retains its moisture. In the 

 majority of woody dicotyledons it is longitudinally entire. 

 The colour of the pith in the succulent shoot, or the young 

 plant, is green, which, as the cells empty, changes to 

 white; but to this there are some exceptions. In the 

 greater number of plants no vessels are perceptible in the 

 pith. Little is known as yet with certainty concerning its 

 functions. The majority of leaves are composed of three 

 distinct parts, one firm, and apparently ligneous, constitut- 

 ing the frame-work or skeleton of the leaf; another, suc- 

 culent and pulpy, fills up the intermediate spaces ; and a 

 third, thin, and expanded, encloses the other two, and 

 forms the covering for both surfaces of the leaf. The first 

 of these parts is vascular, the second cellular, and the third 

 a transparent cuticular pellicle. The cellular substance 

 becomes more compact towards the upper surface, and ia 

 here generally covered by a sort of varnish. Towards the 

 lower surface it becomes looser, and receives those aper- 

 tures which permit the entrance of air. In flowers the 

 calyx is generally of the same construction with the leaves ; 

 but the corolla consists of the most delicate cellular sub- 

 stance, whose inner surface rises in the most delicate pro- 

 minences. The spiral canals of a very small diameter pass 

 singly through the lower part of the leaves of the corolla; 

 and no trace of apertures is to be discovered. The fila- 

 ments have a similar construction ; but the anthers differ in 

 construction from all the other parts. Entirely cellular, 

 they contain, from the beginning, a number of bodies pe- 

 culiarly formed, called pollen. The surface of the female 

 stigma is covered with the finest hairs, which, without a 

 visible aperture, receive the fructifying mass in the same 

 organic way as the hairs of the root receive the moisture of 

 the earth. The ovary contains, before the fructification, 

 merely little bladders, filled with the nourishing juice. 

 After the fructification, the future plant shows itself first in 

 a little point which floats in that juice. Nourished by the 

 latter, the little plant either swells and developes its parts, 

 the cptyledones particularly becoming visible ; or, if the 

 juice is not entirely used up, it coagulates to a body like 

 albumen, and the plant remains in the case of ths.(so called) 

 monocotyledones, undeveloped 



