2,| SCIENCE OF AGRICULTURE. Part II. 



..'■■ lined the Mine molt, deduced from it tun the lame i elusion. We mav regard it, thou, as certain, 



thai i i ol th i - nich u is here represented, though in the progress ol its 



developement, It may atlecl a varletj of directions I d direction of the rool i« generally perpen- 



dicul ir, in which it descends to a coniiderable depth if nol interrupted bj some obstacle In Uking t ij> 



• ii, i thai had been planted in ■ poor soil, Du Hamel found that the root had descended 



alma t, while the height of the trunk m nol more than -ix inches. It the root meet! with an 



icle n then takes ■ horiiontal direction, not by the bending of the original shoot, but by the sending 



ol lateral shoots The same eflfed also follows if the extremity of the root is cut off, but not always; 



for ii i- .1 common thing in nursery garden) t.. cul off the tap-roots of drills of seedling oaks, without 



removing them, bj a sharp spade, and these generally push out now tap-roots, though not so strong as the 



former ' When a root ceases of it- own accord to elongate, it sends out lateral fibres which become 



branches, and are always the more vigorous the nearer they arc to the trunk; but the lateral branches of 



borisontal root, are the less < igorous the nearer they are to the end next the trunk, in the former case, 



the increased luxuriance is perhaps owing to the easy access of oxygen in the upper divisions; but, in the 



latter c ice, the increosi d luxuriance of the more distent divisions is not so easily accounted tor, it it is not 



to l>o attributed to the more ample supply Of nutriment which the fibres meet with as they recede from 



the trunk, particularly if you suppose a number of them lying horizontally, and diverging like the radii of 



■ circle Hut the direction of roots is so liable to be aflbctcd by accidental causes, that there is often but 



little uniformity even In root, nfthe same species. If plants were to be sown in a soilol the same density 



throughout, p rhap- there might be at least as much uniformity in the figure and direction of their root-, 

 a, in those of their branches; but this will seldom happen. For if the root is injured by the attacks ol 

 insects or interrupted by Stones, or earth of too dense a quality, it then sends out lateral branches, as in 

 the , sometimes extending in length, by following the direction of the obstacle, and some. 



times ceasing to elongate, and forming a knot at the extremity. Hut where the soil has been loosened by 

 digging or otherwise, the root generally extends itself to an unusual length ; and where it is both 

 loosened and enriched, it divides into a multiplicity of tibres. This is also the case with the roots of 

 plant- vegetating in pots, or near a river, but especially in water. Where roots have some considerable 

 obstacle to overcome, they will often acquire a strength proportioned to the difficulty: sometimes they 

 will penetrate through the hardest soil to get at a soil more nutritive; and sometimes they will insinuate 

 their fibres into the crevices even of walls and rocks, which they will hurst or overturn. This of course 

 requires much time, and .Iocs much injury to the plant. Hoot- consequent!) thrive best in a soil that is 

 neither too loose nor too dense; but as the nourishment which the root absorbs is chiefly taken up by 

 the extremity, so the soil is often more exhausted at some distance from the trunk than immediately 

 around it Du Hamel regards the -m ill fibres of the root, which absorb the moisture of the soil, as being 

 analogous to the lacteals of the animal system, which absorb the food digested by the stomach : but the 

 root is rather to be regarded as the month of the plant, selecting what is useful to nourishment, and 

 rejecting what is yet in a crude and indigestible state; the larger portions of it serving also to fix the 

 plant in the soil, and to convey to the trunk the nourishment absorbed by the smaller tibres, which, 

 ascending by the tubes of the alburnum, is thus conveyed to the leaves, the digestive organs ot plants. 

 Du Hamel thinks that the roots of plants are furnished with pre-organised germs, by which they are 

 enabled to semi out lateral branches when cut, though the existence of such germs is not proved ; and 

 affirms, that the extremities of the fibres of the root die annually, like the leaves of the trunk and 

 branches, and are again annually renewed ; which last peculiarity Professor Willdenow affirms also to be 

 the fact, but without adducing any evidence by which it appears to be satisfactorily substantiated. On 

 the contrary, Knight, who has also made some observations on this subject, says, it does not appear that 

 the terminating fibres of the roots of woody plants die annually, though those ot bullions roots are found 

 to do so : but the fibres of creeping plants,' as the common crowfoot and strawberry, certainly die annu- 

 ally, as do those of the vine. 



158 ! The slrm. The stem, like the root, or at least the stem of woody plants, is also augmented m 

 width by the addition of an annual layer, and in length, by the addition of an annual shoot bursting from 

 the terminating bud. Is the developement of the shoot issuing from the stem eflected in the same man- 

 ner also- The developement of the shoot from the stem is not effected in the same manner as the 

 developement of that from the root, by additions to the extremity only, but by the introsusception of 

 additional particles throughout its whole extent, at least in its sort and succulent state : the longitudinal 

 extension diminishing in proportion as the shoot acquires solidity, anu ceasing entirely when the wood 

 is perfectly formed, though often continuing at the summit after it has ceased at the base. The exten- 

 sion of the -hoot is inversely as its induration, rapid while it remains herbaceous, but slow in proportion 

 as it is converted into wood.' Hence moisture and shade are the most favourable to its elongation, because 

 thev prevent or ret ird its induration ; and hence the small cone of wood which is formed during the 

 first year of the plant's growth increases no more after the approach of winter, either in height or thick. 

 ness." Such is the mode of the growth and developement of the trunk of perennial and woody plants, to 

 which there exists a striking exception in the growth of the trunk of palms. Their internal structure 

 has been already taken notice of as possessing no concentric or divergent layers, and no medullary canal, 

 but merely an assemblage of large and woody fibres, interspersed without order in a pulp or parenchyma, 

 softer at the centre, and gradually becoming harder as it approaches the circumference When the 

 seed of the palm tree germinates, it protrudes a circular row of leaves, or of fronds, which crowns the 

 radicle and is succeeded in the following year by a similar row issuing from the centre or bosom of the 

 former'leaves, which ultimately die down' to the base. This process is continued for four or five years 

 successively, without exhibiting as yet any appearance of a stem, the remaining bases of the leaves or 

 frond forming by their union merely a sort of knob or bulb. At last, however, they constitute by their 

 union an incipient stem, as thick the first year as it ever is after ; which in the following year is aug- 

 mented in height!] as before, and so in succession as long as the plant lives, the leaves always issuing 

 from the summit and crowning the stem, which is a regular column, but decaying at the end of the year, 

 and leaving circular marks at the points of insertion, which furrow the surface of the plant, and indicate 

 the years of its growth. 



158:3. The branches, in their mode of growth and developement, exhibit nearly the same appearances 

 as the trunk from which thev issue They originate in a bud, and form also a c one which consists of pith, 

 wood and bark ; or rather they form a double cone: for the insertion of the branch into the trunk 

 resembles also a cone a hose base i- at the circumference, and whose apex is at the centre, at least if it is 

 formed in the tir.-t \ear of the plant's growth, or on the shoot of the present year , but tailing -hurt of the 

 centre in proportion to the lateness of Its formation, and number of intervening layers. Branches in their 

 developement assume almost all varieties of position, from the reflected to the horizontal and upright; 

 but the lower branches ol trees are found to be generally parallel to the surface of the soil on which they 

 grow even though that surface should be the sloping side of a hill, owing, as some have thought, to the 

 evolution of a greater number of buds on the side that forms the obtuse angle with the soil, in conse- 

 Quence of it- being exposed to the action of a greater mass of air. 



1584. The bud, which in the beginning of spring is so vary conspicuous on the trees of this country as to 



ihoot 'is produced, it is at the same time furnished with new buds, which are again extended into new 



