564 
composition of water,—the descent of the cam- 
bium and its conversion into wood and bark ;— 
and, lastly, the primary principles of which 
plants consist, or to which they may be reduced, 
—carbon, oxygen, hydrogen, azote.” 
We have discussed the structure of plants in 
the articles Borany, Acoryneponous Puanrs, 
CELLULARES, Composira, CrucIFERoUS Puants, 
Cryprocgamous Puants, DicoryLEponous Puants, 
Enpocens, Exocnns, Lrguminous Puants, Mono- 
COTYLEDONOUS PLANTS, ORGANIZATION, and a great 
many others; the parts, members, and organs of 
plants, in the articles Atr-Vessnns, AnrTHER, 
Artin, ARMATURE, Bark, Burry, Bract, BRancu, 
Bun, Buus, Canyx, CapsuLe, CatKin, CELLULAR 
Tissun, Corona, Cotynepon, Cutm, Down, Epr- 
DERMIS, Frowsr, Fronp, Fruit, Germ, Guanp, 
Invontucrum, Kernen, Lear, Nectary, Nov, 
Ovary, Prrtcarp, Piru, Ponten, Rapicix, Root, 
Sap, Semp, Sponerones, SporE, Stamens, STEM, 
TupEr, VascuLarus, and many more; the con- 
stituents, secretions, and proximate principles of 
plants, in the articles ALBumEeN, ALBURNUM, ARo- 
mA, AsuEs, BAnsams, Biuoom, CAMBIUM, CHLORO- 
PHYLLE, DurAmMEN, Extract, Frsrin, Foop or 
Prants, Guuren, Gum, Lianin, Opour, Orn, PHos- 
PHATES, Proven, Resin, StarcH, Sugar, VEGE- 
TABLE Acrips, ALKALOIDS, TURPENTINE, and a mul- 
titude of others; the general economy of plants, 
or their form, habit, relations, and exterior sus- 
ceptibilities, in the articles AccLIMATATION oF 
Prants, Ace or Prants, Anrtat Roots, Arr-CE1is, 
Arr-Priants, ANALogyY, ANNUAL Puants, AQuATIC 
Puants, Barren Friowers, Brennzan Purants, 
Briancuine, Erronation, Grarrine, Hasrr, Hers, 
Hypripizing oF Prants, Morpnonoagy, Orrset, 
Parasires, Potten, Rotation or Crops, Srep, 
TREE, and many more; the exterior chemistry 
of vegetation, or the controlling influences which 
are exerted over the life and energy of plants by 
external agencies and outward circumstances, in 
the articles Anration, Arr, AGRICULTURAL CHE- 
Mistry, AutitupE, ATMOSPHERE, Cargontc AcID, 
Ammonra, Azotx, Canoric, Crimatn, Foop or 
Prants, Humts, Gypsum, Irrigation, Licgut, Lime, 
Manvrg, PuLVERIZATION, Sort, Sowine, TempERa- 
TURE, WATER, and many others; the organic 
functions and vital actions of plants, in the arti- 
cles ApsorpTion 1n Puants, Aistrvation, Ascent 
or Sap, Camprum, Enposmosn, Huaporation, Ex- 
CITABILITY OF Puants, Excretion or Puants, Fr- 
UNDATION, GERMINATION, GRow TH, IRRITABILITY,- 
Morenonocy, Nutrition, Organic CHEMISTRY, 
SECRETION, VASCULARES, and many more; and the 
diseases of plants in the articles Apuis, BuieHt, 
Canker, Har-Cockis, Decay, Dropsy, Ereot, Ex- 
TRAVASATION, Fascra, GALL, GANGRENE, Honny- 
Drw, Kyor, Mitpew, Smut, and a number of 
others, Any further notice of these multitudes 
of topics, either in groups or in a connecting 
manner, and much more seriatim, would be use- 
less repetition; and, in the sequel of the present 
article, we shall merely notice two or three pro- 
VEGETABLE PHYSIOLOGY. 
minent facts and speculations respecting vegeta- 
ble physiology which happen to have been either 
touched but slightly or not touched at all in 
other parts of our work. 
The peculiar organic action of root crops, in 
its connexion with fallowing effects and with 
the economy of efficient rotations, is a subject 
of great practical interest to farmers; and is 
briefly but luminously discussed in the following 
terms by Messrs. Way and Ogston:—“ Root crops 
are means, when judiciously employed, of in- 
creasing the fertility of the land,—of render- 
ing it, that is, capable of bearing larger crops 
of the more valuable produce, wheat and the 
other cereals, which form the great staple of 
food for man. Now, how do they effect this? 
Whence the efficacy of the turnip and the man- 
gold wurzel. What peculiar properties do these 
roots possess, that their cultivation should form 
so important a feature in modern agriculture ? 
They are most powerful, most industrious agents 
in the collection and preparation of food, both 
mineral and vegetable, for the use of other crops. 
They are continually employed in abstracting by 
their leaves from the air the constituents of 
which their own vegetable substance is made up; 
they never cease to collect by their roots, and 
to bring to the surface, the mineral matters 
which are essential to their own growth and to 
that of the crops which follow them; and both 
these forms of matter, the organic or vegetable, 
and the inorganic or mineral, are (when the crop 
has been consumed by sheep) in great part left 
in the soil in the condition most favourable for 
the purposes of the succeeding plants. It is 
chiefly, however, to the accumulation of vegeta- 
ble matter, that we are to attribute the influence 
of the root crop generally in improving the soil ; 
for although the turnip does certainly add to the 
available stock of mineral ingredients of the sur- 
face soil, its own growth is very mainly depen- 
dent upon the sufficiency of their supply; and to 
obtain a very liberal return, we must be pro- 
portionately liberal in our grants of the mate- 
rials which are indispensable to the construction 
of the crop. Root crops, from the great develop- 
ment of their gas-collecting leaves, are compara- 
tively independent of the soil for vegetable 
nourishment. They may in reality add to, rather 
than take from, the quantity of vegetable matter 
in the soil, even when entirely removed ; for land 
has been found after several years’ cropping with 
turnips, all the produce being carried off, abso- 
lutely richer in organic matter than it was 
at first, the plant having returned to the soil 
more than it had taken from it. How much 
more is this the case when a large portion of 
the organic matter, after passing through the 
body of the sheep, is returned in a highly com- 
minuted state tothe land. It cannot, however, 
be too often insisted upon, that, whilst we may 
fully restore by a green or root crop all the 
organic wealth of which the soil has been de- 
