67 



FARMERS' REGISTER. 



[No.- 12 



same effect may by produced by snow and ice, 

 which, in the winter, frequently accumulate upon 

 young trees, aud the young limbs oi' trees, and 

 bend ihem towards the earth. Thus it is, that 

 though there is a tendency in trees towards a per- 

 fect regularity in growth, so that if they could be 

 freed from the operation of all disturbing causes, 

 they would apoear as if morticed together by the 

 hand of art, aiid would be in their outlines perfect 

 cones, yet we never see them presenting this re- 

 gularity of form. 



There are one or two facts respecting the opera- 

 tion of these disturbing causes, which are worthy 

 of a passing notice. One ol them is, that most 

 of them operate more powerfully in the winter 

 than in the summer. Totliis, as well as to the fact, 

 that they are longer exposed to this operation, 

 must be attributed the far greater irregularity whicii 

 we observe in perennial than in annual plants. 

 The catnip, (iiepeta cataria,') which has none of 

 these disturbing causes to contend with, except 

 those which operate in the summer, and these 

 only for a short period, presents but slight devia- 

 tions from its regular form ; whilst the oak, which 

 lives from year to year, and from age to age, bear- 

 ing the storms of a hundred winters, is well cha- 

 racterized as the "gnarled oak," Another fact 

 worthy of notice is, that although the operation of 

 these causes seems to be in the strictest sense ac- 

 cidental, so that we can assign no reason why one 

 bud should be destroyed rather than another, or 

 why an insect should sting one branch rather than 

 another ; that yet their destroying effect is so ma- 

 naged as to be consistent with a general regularity 

 of growth. About as many buds are destroyed 

 on one side of a tree as on another. Seldom, if 

 ever, do we meet with a tree so lop-sided (to use 

 an unauthorized but very expressive word,) as to 

 endanger its stability. Although a tree is very 

 irregular in the minutiae of its growth, yet it is re- 

 gular in the midst of all its irregularity. 



Chap. IV. 



PRINCIPAL OFFICE OF THK ROOT. SPONGK- 

 LETS. BIENNIAL ROOTS. COLLAR OF 

 PLANTS. UNnER-GROUiVl) STEMS, TIIEIU 

 NATURE AND STRUCTURE. 



Having attended to some of the more impor- 

 tant characteristic features of the root, we will 

 now examine that organ a little more in detail. 

 The root of the garden bean (vicia faha) may be 

 assumed as the type. The root of this plant con- 

 sists of a main stem, irregularly divided, and sub- 

 divided, into what are called the branches of the 

 root, or rootlets. From tiiis, which is by far the 

 most common form of the root, we meet with 

 many departures. The root of the carrot, (dau- 

 cus carota) consists of a mass of vegetable mat- 

 ter, of a conical form, and having all its rootlets at 

 its lower extremity. In the turnip (brassica rajxi) 

 this mass is nearly globular in its form. Most 

 grasses have no regular main-root, but a number 

 of rootlets starting from one common point, the 

 base of the stem. Lichens have no regular root ; 

 but the whole of the lower surface of their leaves, 

 lying in contact with the ground, or rock, or bark 

 ou which they grow, absorb nourishment for them, 



and thus perform the office of roots. There are 

 many modified forms mentioned by botanists ; but 

 as they are very uncommon, it is not worth the 

 while to mention them, when our object is an ex- 

 amination into the physiology of plants. 



The principal office of the root, is to absorb 

 nourishment from the soil. This absorption is not 

 efl'ected by the mass of the root, and throughout 

 its whole length, as is generally supposed, but by 

 a peculiar class of organs, situated along the 

 smaller sub-divisions, or rootlets only. It is some- 

 what difficult to get a distinct view of these or- 

 gans. So long as the root remains buried in the 

 moist earth, they are distended by the liquids 

 which they contain, and which they absorb rapid- 

 ly from the soil. In order to fit them for the per- 

 formance of their appropriate work, they have ne- 

 cessarily been made permeable to liquids in the 

 highest degree ; and hence, when taken out of the 

 ground, and exposed to the dry atmosphere, suf- 

 lering these liquids to pass out, with the same fki- 

 cility with which they passed in, they soon shrivel 

 up, and lie so close to the main root, as to be with 

 dilTiculty distinguished fi'om it. The easiest way 

 to get a sight of them, is to place the root of a 

 growing plant in water, wiiich in this instance, 

 may be considered a transparent kind of soil ; in 

 such circumstances they (luickly become distend- 

 ed, and stand out visibly from the side of the root- 

 let. From a similarity in the structure of these 

 organs, as exhibited under the microscope, as also 

 in their manner of action, to little sponges, they 

 have received the name of spongioles or sponge- 

 lets ; and by this name we shall hereafter men- 

 tion them. 



That roots absorb nourishment solely by means 

 of their spongolets, Senebier has proved, by the 

 following simple experiment. He took two young 

 radishes (raphanus saiivus') from llie ground, 

 with their stems and leaves ; one was so placed 

 that its apex only fthe part on which the sponge- 

 lets are situated) dipped in water; the whole root 

 of the other was plunged beneath the surftice of 

 the water, excepting the apex, which was exposed 

 to the air. The leaves of the former, remained 

 fresh for several days, whilst those of the latter 

 soon began to wither, and only recovered their 

 freshness, when the extremity of their root was 

 immersed. This is an experiment which has 

 been frequently repeated, and always with similar 

 results. 



The form of the sponglets of plants, which de- 

 rive their nourishment immediately li-om the soil, 

 is always spherical or spheroidal. In that curious 

 class of plants termed parasites, (of which the 

 misletoe may be mentioned as an example.) which 

 instead of searching in the earth lor their own 

 food, fix themselves upon the stems of other plants, 

 and live by robbing, the spongioles have the form 

 of disks ; thus fitting them to (asten themselves to 

 the stems of other plants, and also to absorb the 

 greatest quantity of nourishment from those plants. 

 Spongelets in this form, fasten themseh'es to the 

 stems of plants, in just the same way in whicli 

 children fiisten moist pieces of leather to stones, in 

 order to lift those stones. 



Spongelets as I have already remarked, are 

 situateci only along the smaller sub-divisions of 

 the root. A knowledge of this ftict, will suggest 

 several rules to be observed in the cultivation of 

 plants. First, when manure is used to assist the 



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