246 



m [ENCE OF AGUICULTURE 



Taut II. 



' . in .1111.111 iK which attends tome perennials, ii at firattplndle-chaped and per. 



pendicular, sending out me lata ral Bbn -, but dies .it the lower extremity in the course of the succeed- 

 ing winter, and protrudes new Bores from the remaining portion, and even from the lower portion of (he 

 stem, in the courserol the following spring, which, by di icending into the soil, draw down the plant with 

 them, so thai i*nt of what was formerly item is now converted into root This process is repeated every 

 ind by consequence ■ portion of the item Is made to descend every year Into the earth. The 

 anomaly ma] hi' exemplified in the roots of Valeriana dioii a, I - and O'xalis .\<-« tosi Ua ; 



and will also account tor tin' bitten and truncated appearance of Scabil -a mi i Isa, or devil's hit. 



1594 lligrat ri/ roott depend on a principle limilai to the foregoing, if the stein of a descending root 

 happens tone creeping or procumbent instead of heme erect, then the lateral shoots from above are carried 



forward in the direction of that prociiinbeiiiv. so that in the course of a lew \ears the plant has actually 



i i it. place by so much aa the stem has been converted into a root Thisia well exemplified in the 



genus /Vis, a plant of which, as it enlarges in circumference, dies in the centre, and presents a ring of 

 plants instead of a will in one. In the case of some aquatics, which float ahout on the surface of the 



water M thej happen to be driven by the winds, the whole plant may be said to be migratory, as in the 

 genus /..'lima, and tome marine plant-. 



Tin- beet-root, if dissected when about a year old, presents the singular anomaly of being already 

 furnished with from five to eight distinct and concentric circles of longitudinal tubes or sap-vessels, im- 

 bedded at regular intervals in it~ pulp; whereas other biennial roots form only an individual circle each 

 nd are, consequently, at no time furnished with more than two. 

 1596. Boot* changed to branches ami branches to touts. If the stem of a young plum or cherry tree, but 

 particularly of a willow, i- taken in the autumn, and bent so as that one half of the top maybe laid in the 

 earth, one half ot the root being at the same time taken carefully out, but sheltered at first from the cold 

 and then gradual!] exp Bed to it, and the remaining part of the top and root subjected to the same process 

 in the following year, the branches of the top will become roots, and the ramifications of the rout will 

 become branches, protruding leaves, flowers, and fruit in due season. 



1597. The stem. If the stem of a tree planted by a pond or river is so bent in its 

 growth a- to come near to the surface of the water and to be occasionally immersed in it, 

 it will sometimes semi out from the under surface a multitude of shoots that will descend 

 into tbe water, and develope themselves in the manner of the fox-tail root. Sometimes 

 it happens that a stem, instead of assuming the cylindrical form common to the species, 

 assumes a compressed and flattened form similar to the herbage of the Cactus, as in the 

 lir tribe, ash, &c. 



1596. The anomaly nf the flattened stem {Jig. 190.) is accounted for by Du 

 Ilaiucl.liy supposing that an unnatural junction must have taken place in the 

 leaf-hud ; and so uinled shoots that would otherwise have been distinct. 

 Sometimes the stem i* disfigured by accidental tumours or bunches projecting 

 from the surface, and forming ultimately what are called knots in the wood. 

 They are very common in the oak and elm, and are produced, perhaps, by 

 means of some obstruction in the channel of the sap's motion, by which the 

 ^e>-els become convoluted and swell up into a bunch. 



I hit bunches are also to be met with on the stems of herbaceous plants, 

 as on that of the Carduus pratensis; of which you will often find a portion 

 near the top swollen out into an egg-shaped or egg-oblong hunch, extending 

 from an inch to two inches in length, and about an inch across. If this 

 bunch is cut open in the month of August, it will be found to contain several 

 large and white maggots. It has consequently been occasioned by the 

 puncture of the parent insect depositing its eggs. It does not seem to affect 

 the general health of a vigorous plant, though it might prove seriously in- 

 jurious to a weak one. 



1(100. Bundled stem. Sometimes two or more contiguous stems, extending 

 in the process of their growth till they meet and press against one another, 

 become incorporated at length into one, and form a sort of bundle. This is 

 what may be termed a natural graft, in opposition to an artificial graft, of 

 which it is the model and prototype. The natural graft is always effected 

 by means of the union of the liber of the respective stems composing it ; so 

 that the perfection of the art of grafting consists in applying the liber of the 

 graft and stock together, in such a manner as shall most facilitate their, 

 incorporation. 



1601. The branch. If the branch of a tree is situated, as in the foregoing case of the 

 stem, so as to he partially or periodically immersed in water, it will send out also the 

 same sort of brush-like shoots. 



1602. Bunches or knots, exhibiting a plexus of young shoots (Jig. 191. a) issuing from nearly the same point, 



crossing in all directions, and finally incorporating together by means of a sort nf natural graft, frequently 

 disfigurethe branch. These bunches are frequently to be met with on the branches of the birch tree, and are 



