BOTANY. 



591 



whether while the tree is standing, or after it is put 

 to use. 



The foregoing remarks include a brief description 

 of the phenomena of vegetable growth, and involve 

 the intricate question what is vegetable life ? From 

 the facts adduced relative to vegetable organisation 

 and expansion, we can only venture to assume, that, 

 notwithstanding much may be traced to combined 

 chemical and physical action, we must admit the 

 existence of avital principle which seems independent 

 thereof ; more especially in its power of existing for 

 ages unimpaired in the bowels of the earth ; and, 

 while thus dormant, may be deemed an excitable or 

 fermentable fluid, contained in an organised expan- 

 sible body. 



It is thus assumed, that all and every vegetable 

 membrane, organ, or member, has rudunental exist- 

 ence before expansion. This is perfectly evident on 

 dissection of any gross-growing plant. The flower 

 of a bulb may be seen in the bosom of its invest- 

 ments long before it comes into view ; so may the 

 flowers of fruit trees be detected with the assistance 

 of a microscope, twelve months previous to the 

 bursting of the diminutive bud which contains them. 

 Not only is it quite obvious that no plant whatever 

 can come into existence unless from a seed, a sporule, 

 or from a pre-existing part of itself, so neither can 

 any one membrane of a vegetable body gain identity, 

 unless from a pre-existing rudimental source. 



It may be asked, what then, arc all vegetable 

 accretions only distensions or expansions ? From what 

 has been already stated, we must be of opinion that 

 growth is nothing more or less than simple develope- 

 nient. Whatever vegetable, or part of a vegetable 

 we attend to during growth, the only perceivable 

 change is from small to greater bulk, only from 

 indistinct to evident and appreciable formation. The 

 small shoot, leaf, or flower, is as perfect in its first 

 visible state, as it is after full amplification. While 

 the influences of air, and heat, and light, are acting 

 on the elastic fluids of the system, the cellular and 

 vascular membranes are elongated, and enlarged in 

 definite order ; the enlargement and inflation of the 

 membranes being filled up by the induction of the 

 elemental food imbibed from the earth and atmo- 

 sphere. 



This appears all very feasible in regard to the 

 exterior accretion of plants ; but what can be said of 

 the interior growth that of the new zone of wood 

 for instance. It must be confessed that there is some 

 difficulty here ; principally because it is an invisible 

 process. The fact that a new layer of white wood 

 or alburnum is formed every summer, is known to 

 every body ; but whence it is derived, or how it is 

 formed, is still involved in obscurity. By some phy- 

 siologists it is supposed to be generated by the sap ; 

 which after perfect elaboration becomes coagulated 

 into woody substance. Others suppose that the 

 new zone of alburnum is formed by woody fibres, 

 which descend from every bud above, in the same 

 manner as seeds or cuttings send down fibrous roots 

 into the earth. One contends, that it is a dilatation 

 of the last year's alburnum ; while another insists 

 that it proceeds from the liber. 



Without attempting a long drawn out refutation of 

 the above suppositions, let it suffice to mention only 

 a few facts bearing on some of the ideas, and a few 

 doubts relative to others. The liber which comes 

 into view at the end of the preceding summer, remains 



distinct aud unchanged for many years after its first 

 appearance ; (instance the numerous layers of liber 

 or inner bark of the common lime, or linden-tree, of 

 which Russia mats are made) so that it is an error 

 to imagine that the new alburnum is formed from 

 liber. Neither is it a dilatation of the alburnum. 

 This has been proved a hundred times by experi- 

 ments of marking the last formed alburnum, which 

 marks ever after remain undisturbed, though covered 

 by the succeeding layers of new wood. That the new 

 layer is formed by fibrous processes descending from 

 the buds is plausible, if we only consider a stem or 

 trunk of a few feet in length ; but when we see the 

 new layer of alburnum forming at the bottom of a 

 lofty tree, almost as soon as it appears in the imme- 

 diate neighbourhood of the buds, we have reason to 

 doubt whether actual fibres can possibly reach so far 

 down in so short a time, as intervenes between the 

 bursting of the buds and the appearance of the 

 new alburnum so far below. Another thing rather 

 in favour of this notion, is, if the attachment of a 

 bursting bud be examined, there are seen prominent 

 bundles of fibres, apparently descending from the base 

 of the bud, and disappearing downwards on the 

 surface of the last year's alburnum. Whether these 

 processes actually descend, or whether they are sap 

 ducts, enlarged as they approach the craving outlet, 

 is, perhaps, questionable. At any rate the supporters 

 of this opinion must know that the buds, which burst 

 into shoots in this year, are the production of, and 

 attached to, the alburnum of the last year ; and there- 

 fore cannot directly serve to increase the alburnum 

 formed in this. The next idea relative to the accre- 

 tion of alburnum yet to be noticed, is that which 

 attributes the formation of wood, and indeed every 

 other member of the plant, to the organisable pro- 

 perty of the perfect sap. This fluid, it is said, after 

 being elaborated in the leaves, returns down into the 

 space between the last year's alburnum and liber ; 

 and there losing its fluidity, becomes pulpy or granu- 

 lated, and by some other consolidating process is 

 changed into a ligneous consistence, and into all the 

 varied structure, viz. cells, tubes, air-vessels, and 

 fibre of perfect timber. 



Whether a fluid purely homogeneous, like the sap 

 of plants, be capable of transformation into regularly 

 organised matter, is a circumstance of which, per- 

 haps, we have no parallel instance in nature. Even 

 with the assistance of all the great natural agents, it 

 is not probable that the simplest plant, or the simplest 

 organised part of one, can come into existence for- 

 tuitously. We would therefore infer, that as all plants, 

 and parts of plants, arise from a rudimental organised 

 source, the new layer of alburnum has a similar 

 origin ; and that vegetable physiologists will in time 

 be able to detect the source, and be able to show it 

 in winter as well as in summer : for throughout the 

 latter season, while in the state of what is called 

 cambium, it is not only visible, but tangible, though 

 wholly imperceptible to the naked eye in winter. 



Having taken a brief view of the phenomenon 

 called growth, we may next advert to that principal 

 component of plants commonly called the sap. This 

 is so intimately connected with vegetable structure, 

 and evolution, that it is impossible to understand the 

 developement of the one without appreciating the 

 nature and uses of the other. As plants are com- 

 posed of a vast assemblage of cells and vessels, fluids 

 either gaseous or aqueous are necessary for their dis- 



