BOTANY. 



The famous chesmit tree oa Etna (Centum Cavalli), 

 hjraiolog-y. is one of tliosc extraordinary productions of nature, 

 v - though scarcely more so than the celebrated pear 

 trie in Herefordshire. But the most extraordinary 

 vegetable production of which we know any thing, 

 is the Aiiuimoniu il/gitata, a native of Africa. Its di- 

 ameter is said to be 30 feet, and its circumference 

 90 feet. Its branches are from 30 to 60 feet long, 

 and the hollow of its trunk is the habitation of 

 many negro families. 



fae tribe. The pine tribe ( arborcs acerosce ) has many branches 

 which evolve buds at their extremities ; the central 

 bud grows in a straight direction, while the others 

 surround it in a whirl, (Part I. Sect. ii. Art. 15.) 

 Wnclitt. All these varieties of the ligneous stem send out 

 branches without any particular order : it may be re- 

 marked, however, that although no particular ar- 

 rangement can be perceived in individual trees, yet 

 each genus has a distinctive form and arrangement, 

 winch are more easily known than described. Thus 

 the most inattentive observer must have been frequent- 

 ly struck with the difference of the characters of the 

 oak and of the elm ; but the most accurate philoso- 

 pher would find much, nay, insurmountable difficulty, 

 in saying wherein that difference lies. Branches are 

 supposed to arise from a convolution of vessels ; so 

 long as the vascular bundles proceed in an uninter- 

 rupted straight line, so long will the stem remain 

 straight ; but whenever they form a knot, nature ap- 

 pears to make new efforts, and- a branch is produced. 

 Branches may be induced by lopping, or by making 

 transverse incisions, which, by checking the regular 

 course of the sap, may cause the convolutions of the 

 vessels. Brunches may be considered in all other re- 

 spects similar to the main trunk of the parent stock. 

 Vorns. Thorns are stunted branches; their imperfect form 



may be owing to the buds being partially evolved, 

 from a want of proper nutrition. Indeed, that it is, 

 in a great degree, owing to such a cause, is proved by 

 the conversion of thorns into branches on removal in- 

 to richer soil. This fact is well known to gardeners, 

 as many fruit trees, which are thorny when wild, be- 

 come smooth when cultivated. Sometimes ihe foot- 

 { stalks of pinnate leaves that have fallen off become 



thorns, as is the case in the Astragalus Traaucaniha. 

 cities. Prickles may be taken off with the bark, and is 

 therefore a mere elongation of that organ, which is 

 chiefly composed of cellular substance, and of the cor- 

 tical vessels. There is this remarkable distinction 

 between the prickle and the thorn, that no cultiva- 

 tion whatever can convert the former into a shoot, 

 as is the case with the latter ; for the vessels become 

 very rapidly hard, separate from the stem, and at last 

 is merely retained by the exterior covering. The 

 stipules of some plants are converted into prickles, as 



!, Ter . inBcrtieriivulgarii. The flower- stalk and foot-stalk 

 are also composed of cellular texture, of central and 

 utalk. cortical vessels, which convey the vegetable juices to 



and from the leaf. 



* drils. Tendrils have the same structure as the preceding, 

 and are in fact elongated foot-stalks, without the 

 leafy expansion, which adds to their length ; and be- 

 ing unable to support their own weight in a straight 

 Ifae, they assume the spiral form. Willdenow ascribes 



a considerable influence ta tlie current of air in deter- Vcgc; 

 mining the direction of the tendril. l'l,y,u,logy. 



The stem of palms has received many names, be- p a | Itl ^~ 

 ing sometimes considered a mere variety of the lig- 

 neous stem ; at other times it is called a stipe, and 

 described as differing in all its essential characters 

 from every species of ligneous stem. This latter opi- 

 nion has been most generally adopted by foreign bo- 

 tanists, particularly those of France. M. M. Mirbel, 

 Gerardin, Desfontaines, and Daubenton, have treat- 

 ed this subject with much acutcncas; but they seem 

 to rest too much on the division into monocotyledons 

 and dicotyledons ; we shall therefore confine our- 

 selves chiefly to the consideration of the facts which 

 they have developed, and leave the discussion of the 

 theoretical views to those more disposed to engage 

 in a wordy warfare. The stems of palms as well 

 as of all those plants which are included under 

 the monocotyledonous class, are formed of the foot- 

 stalks of the leaves. This idea was anticipated 

 by Linnaeus long ago, and has since been confirm- 

 ed by the inquiries of the gentlemen already refer- 

 red to. Although the genus of palms is the lof- 

 tiest, and, in some instances, the most long-lived 

 of the vegetable kingdom, which justly entitle them 

 to the name of trees, yet they are in fact simple 

 perennial and herbaceous stems, as they have no- 

 thing in common with ligneous stems. The sue- Formation, 

 cessive addition of circular crowns of leaves, with- 

 in each other, gives origin to the thickness of the 

 woody trunk, at the same time the lateral increase is 

 restricted by the preceding band ; but the powers of 

 life being thus confined, additional force is given to 

 the vertical increase, and thus the enormous height of 

 the palm tree is produced. Mirbel says, that the 

 palm " is less a stem than an immense bundle of the - 

 toot-stalks of radical leaves." Each series of vessels 

 is wholly independent of all the others, each having 

 been separately formed. There cannot, therefore, be 

 any regular aggregation of woody circles. The ves- 

 els probably are similar to, and perform, the same 

 functions as those of the trunks of trees, modified by 

 the peculiarities of the palm. The growth of the 

 whole of monocotyledons is nearly the same, and the 

 folium candidnm, when cut across, will exhibit every 

 character of the class. 



The other kinds of stems, such as the Culm, the Other 

 Stipe, (thestemof.Ftfw.g'i'and Filices), and the Bristle, kind* of 

 are supposed to correspond with monocotyledons in stems - 

 general ; but the parts of most of them are so ex- 

 tremely minute, that much must be left to the imagi- 

 nation of the observer. 



Thus, the stems of vegetables may be arranged ac- ciassifica- 

 cording to the density and perfection of their compo- tion." 

 nent parts, or according to the character of the seeds 

 from which they have been derived ; the firm stems t 

 with all their organs perfect, being derived from di- 

 cotyledonous, and the more loosely compacted from 

 monocotyledonous seeds. The latter classification, 

 however correct, does not seem so natural as the for- 

 mer, which fixes on the external characters of the 

 part itself, at the very period of its existence at whicli 

 Jt is described, by which means all ambiguity is avoid- 

 ed, and the description obvious to aJl, It rs willingly 



