BOTANY. 



rable valuf to the practical gardener, particularly 

 liim who wishes to bring tin- vegetable productions 



*~*'~ l ' of every part of the world into one spot. Various 

 schemes have been devised for eflecting this ; and 

 none appears to us better adapted to attain the end 

 in view, than that which is described by Gerardin, as 

 having been adopted by M. Thouin, professor of the 

 cultivation and naturalization of exotic plants in the 

 museum of natural history in Paris. The principle 

 on which his arrangement is founded, is the difference 

 of temperature produced by different aspects, and by 

 a proper distribution he lias succeeded in his attempts. 

 The details of the scheme are given by Gerardin, in 

 the 1st vol. of his Essai dc Physiologic Vcgclalc, to 

 which we beg leave to refer. 



Ippen- Besides the seed itself, there are some appendages, 



of which it will be necessary to give an account 

 (Part I. Sect. ii. Art. 2.) 



Irillus. To this class belongs the arillus, which varies 



considerably in different seeds, and appears desti- 

 ned to protect them. Much has been said on the 

 proper application of this term ; and it must be con- 

 fessed, that it requires no small share of discrimina- 

 tion to detect the minute circumstances which fix the 

 character. Dr Smith has made some valuable remarks 

 on this subject in his Introduction to Botany. 

 P us - The pappus (Part I. Sect. ii. Art. 3.) is evidently 



intended to transport the seeds to which it is attach- 

 ed, to situations distant from their native spot. 



The uses of the tail and tuft seem to be analogous 

 to those of the pappus. Those of the beak, crest, 

 and ribs, are not so evident. 



SECT. II. The Hoot. 



>ot. THE root may be considered the first complete part 

 of any vegetable production. We shall trace it from 

 the state of the radicle to the period of its greatest 

 perfection. 



The root varies in different plants, both in point 

 of external character, and in the period of duration, 

 (Part I. Sect. ii. Art. 4.) The roots of those plants 

 J. that live only one year are called annual; of this kind 

 al. is barley : The term biennial is applied to such as are 



E reduced in one year, and do not flower and bear 

 uit until the following year, as is the case in com- 

 ennial. mon wheat : And those arc called perennial, that live 

 and blossom for many successive years, such as trees 

 and many herbaceous plants. The term biennial is 

 also applied to any plant that is produced in one 

 year, and flowers in another, provided that it only 

 flowers once. " This," sayg Dr Smith, " is often 

 the case with iheLavatera arborea, or tree mallow, and 

 some other plants, especially when growingout of their 

 natural soil or situation. Linnaeus," he adds, " justly 

 observes, that however hardy, with respect to cold, 

 such plants may prove before they blossom, they pe- 

 rish at the first approach of the succeeding winter ; 

 nor can any artificial heat preserve them." This phe- 

 nomenon, with great probability, the Doctor refers to 

 the " exhaustion of their vital energy by flower- 

 ing." It is a singular, but, at the same time, per- 

 fectly well ascertained fact, that many perennial 

 plants, natives ot warm countries, become annual, 

 when introduced into colder climates, as the Trop<eo- 



\OL. IV. FART I. 



II'/IIH, i.r j'-p.n'.en Nii.iliti-liiint. The fibrous radicles, Vegetable 

 (Part I. Sect. ii. Art. 4.) wiiii-h only are called Wi y si<: */ 



it8 by physiologists, are in every case annual ; '~ 



a circumstance particularly to be attended to in 

 transplanting. The winter season is the most suit- 

 able to this operation, because at that time the 

 fibres are either dead o torpid, and the whole vital 

 powers of the plant are dormant ; the separation of 

 the radicles, therefore, cannot be injurious, but as 

 soon as young radicles put forth, the plant cannot be 

 removed without irremediable injury. Very young 

 annual plants may bear it, if their leaves be kept well 

 moistened, as they form radicles with remarkable fa- 

 cility. 



Grew, to whom the science of vegetable physiolo- Structure. 

 gy is probably more indebted than to any other in- 

 dividual, gave the first accurate account of the struc- 

 ture of roots ; and although his solutions of the va- 

 rious phenomena do not always appear correct, yet his 

 accuracy is uniform, and no erroneous details have been 

 detected by those who have followed his footsteps. 

 As far as we know, there has yet been no minute an- 

 atomical description yet given of the radicle, it being 

 generally supposed to consist chiefly of cellular sub- 

 stance and vessels. Mr Knight has not long ago 

 thrown out the idea, that the rostel is merely a preli- 

 minary organ, at the end of which the radicle is 

 formed, while its own growth is carried on by the 

 increased size of parts already formed. The radicle 

 and root, on the other hand, according to the obser. 

 vations of the same intelligent and accurate philoso- 

 pher, are formed by successive additions made to their 

 extremities, and consist merely of cellular substance, 

 in which certain vessels are gradually formed and per- 

 fected. When the root has arrived at its perfect 

 state, it consists of those parts which are obvious 

 and separable, and of a more minute structure, re- 

 quiring close examination. The distinct parts are the 

 epidermis or cuticle, the outer bark, the inner bark 

 or liber, the alburnum or soft wood, the wood, and 

 the pith. 



All plants, as well as animals, are covered with a Cutick. 

 delicate membrane, which is called the cuticle or epi- 

 dermis ; this is supposed to be formed by the ex- 

 ternal coats of the cellular membrane. In both cases 

 it serves to protect the more delicate vessels, as well , 

 as to transmit freely, by means of its pores, any ex- 

 haled fluid. The analogy between the cuticle of 

 plants and animals is very striking, and may be traced 

 through a vast variety of ramifications. It is said, 

 and we believe correctly, that " the cuticle admits of 

 the passage of fluids from within, as well as from. 

 without ; but in a due and definite proportion in 

 every plant." Light probably acts through the cuticle 

 of such parts of vegetables as are exposed, as it is a 

 transparent membrane. 



Similar to the Pete mucosum of animals is the cellu- 



larintegument.or the Enre/uppe cetliilaireof Duhamel, integu- 

 and Tissu herbace of Mirbel, winch lies immediately ment. 

 below the cuticle. Little or nothing is known of its 

 functions., Duhamel supposed that the epidermis was 

 formed by this pulpy substance ; but Dr Smith has 

 shewn this to be improbable, as it always exfoliates 

 when the outer covering has been destroyed. Very 

 little attention has hitherto been paid to this organ, 

 G 



