16 



FARMERS' REGISTER 



[No. 1 



and transmitting the fluids of plants, the cellular 

 tissue is the principal instrument in their elabora- 

 tion; that is, in the conversion of the crude sap 

 into the sugary, resinous, oily, acid and saline ve- 

 getable secretions. 



The next in order, of the elementary organs of 

 plants, is the woody tissue. Tliis consists of slen- 

 der, tough tubes, tapering lo sharp poinis at each 

 extremiry. These little tubes are so placed, as 

 that the end of one overlaps that of another ; and 

 in this way they form long fibres, running length- 

 wise through the plant."" The fibres of hemp, 

 (ci)imabissativa,) or flax, (liiiumusiialisslmum,) 

 may be selected as good specimens of woody 

 tissue. If we examine, with a good microscope, 

 the finest filament ol flax, we will find that it is 

 not a simple fibre, but is made up of numerous 

 fibres of difierent lengths, very closely joined to- 

 gether, and overlapping each other by their slender 

 extremities. By continued maceration in water, 

 or by boiling in very dilute nitric acul, their cohe- 

 sion may be destroyed, so that by careful man- 

 agement, the simple vessels may be obtained m a 

 separate state. In hem[), their diameter is about 

 six times less than that of a common sized human 

 hair ; in many plants, however, it is somewhat 

 larger than this. These vessels, as has been 

 mentioned, are hollow tubes. For a long time, 

 they were believed to be solid ; but more carelul 

 examination has shown that, in this particular, the 

 early botanists were in error. Tlie great use ot 

 the woody fibre, is, to protect the more delicate 

 organs, and to give sirenglh to every part, of the 

 vegetable structure. It may be considered the 

 bony system of plants. It" it were not tor it, the 



main stationary in the veins. Harvey had become 

 acqainted with the nature of pumps and the struc- 

 ture of valves— when carefully dissecting a human 

 body, he noticed that there were valves, placed at 

 certain points along the principal arteries. The_ 

 only use of valves, is to prevent the return of 

 fluids alter they have been forced out of their most 

 natural position; or in other words, valves are of 

 use only in connexion with circulating fluids. 

 From the existence of valves in the arteries, he 

 infiirred that the fluid which those arteries contain- 

 ed, must circulate through them; from the struc- 

 ture of those vessels, he interred their oflice, and 

 subsequent observation and experiment have fully 

 established the correctness of his inference. On 

 similar ground we infer, that the fluids of plants 

 circulate through the woody tissue; although we 

 have never been able, by direct observation or ex- 

 periment, to prove that they do. In fact, all the 

 elementary organs of plants are so simple in their 

 nature, and so much resemble each other in their 

 structure, that it is not at all improbable, that one 

 organ sometimes performs the work which more 

 properly belongs to another. 



The third and last of the elementary organs of 

 plants, are the vessels of the vascular lissue. 

 These are principally of two kinds : first, spiral 

 vessels, and second, ducts. A spiral vessel la 

 composed, either of vegetable fibre coiled in the 

 form of a wiie-spring,"and with the edges of its 

 contiguous coils adhering together, so as to form 

 an ulibroken tube ; or else, partly of membrane 

 and partly of fibre ; the tube itself being formed 

 of membrane, and the fibre coiled along its inner 

 surliice, so as to give it elasticity and strength. 



boiiv system 01 plants, ii u weie nui lui u, i..v. ^.^...>^., -- .=- .„q..„ .. _„ _, ^ 



stent of an oak would be as brittle as that of alt is easy to get a sight o! his fibre n t e way 

 mushroom ; but lyin.- as it does across the cellu- mentioned when treating of vegetable fibie , but 



lar tissue, it binds it together, and renders all the 

 parts tough, by its own elasticity and strength. 



It occurs in what is commonly c;illed the wood 

 of the plants of which it forms the principal part; 

 in the bark, in small quantities; in the veins of 

 the leaves, and in the husk of most fruits, it ap- 

 pears highly probable, that in addition to the uses 

 just memioned, woody fibre has the office of con- 

 veying fluids in certain directions. The fact that 

 the extremities of its tubes are closed, instead of 

 forbidding, favors such an idea, as we shall hereaf-_ 

 ter see. It is true, that from the impossibility of 

 observing the progress of fluids, in parts so minute 

 and so easily injured as the vegetable tissues, no 

 one has been able to demonstrate this by direct 

 observation. Yet we can hardly doubt that such 

 is the case, when we consider how rapidly the 

 sap flows up the stem of a tree, which consists to 

 a very large extent of woody fibre; and lurther, 

 that when colored infusions are made to enter 

 plants, they are uniformly found to pervade the 

 parts composed almost entirely of woody fibre. 

 We may draw an argument to support the same 

 notion, from the structure of the woody lissue. 

 Its structure is such as fits it for this oflice ; and so 

 universally do we observe in nature an adapta- 

 tion of means to their ends, of structures to their 

 otTices, that we may, with very little danger ofer- 

 ror, infer the one f>om the other. An instance of 

 such an inlerence, which will, perhaps, show the 

 value of such reasoninji as this, better than any 

 o-eneral remarks, is allorded in the discovery of 

 The circulation of the blood of animals. Cefure 

 the lime of ilarvcy. the blood was believed lo re- 



in this way, we can obtain no correct idea of the 

 structure of the spiral vessels. By carefully dis- 

 sectinir a boiled stem of asparagus, we can exam- 

 ine them, in their natural condition. Spiral ves- 

 sels are found in plants during every period oi 

 their growth; even in theplantule, orembno in the 

 seed. They stretch through the whole length of a 

 plant, from the root, to the extremity of the leaves. 

 They are generally disposed in bundles, along 

 with ducts and woody fibre; each bundle contain- 

 ing from three, to one hundred. In succulent 

 plants they are found in every part of the stemj 

 in woody plants, they always surround the pith, 

 and form a part of the mid-rib of the leaves; they 

 are also found in the difierent parts of the flower 

 and seed. In diameter, they vary fi-om three, to 

 one-thousandth of an inch. In llowerless jjlants, 

 such as mushrooms, lichens, &c., they are entire- 

 ly wanting; from this it is interred, that they are 

 connected in some unexplained way, with the pro- 

 duction of flowers and regular seed. 



II a stem be cut across under water, air bub- 

 bles immediately form at the months of the spi- 

 ral vessels; hence it is inferred that their peculiar 

 oflice is that of transmitlinn; gases through |)lants. 

 Some botanists speak of them as the trachece, or 

 wind-pipes of plants. When we call to mind 

 how lai-ixe a portion of every vegetable structure 

 is composed of oxygen and hydrogen, and also 

 how lafiie a portion of the carbon of plants is ob- 

 tained immediately from the atmosphere, we will 

 not be surprised that a class of vessels is set apart 

 Ibr the conveyance of gases. Their structure is 

 admirably adapted to their ollicc. Had they bceu 



