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ART. II. Retrospective Criticism. THE Study of Bees, and of Chemistry and Vegetable Physiology. (p. 576.)-1 would be sorry if Mr. Wighton should think I undervalued the study of bees. I certainly did not mean to express myself in that way. He seemed, how. ever, from his manner of expression, by boasting of an ignorance of alkalies, to undervalue the study of chemistry. I certainly was not of opinion that his pretended ignorance was real, but thought it proper to defend the necessity of the knowledge of chemistry, to a certain extent, to gardeners. There may be differences of opinion as to the comparative space that chemistry ought to occupy in the education of a gardener ; but, certainly, it was not rating it too high, to wish a tithe of the time bestowed by Mr. W. on bees to be devoted to that purpose. His work lately published on bees bears evidence of its having originated in a vast deal of attention to the subject. In many situations, however, it may be found that a knowledge of chemistry is of more consequence, in others it may not; education should be as much as possible suited to the future prospects in life ; and much more attention may be required, in particular instances, to certain branches than to others. Gardeners, however, as at present situated, are subject to so many changes of place, that a very extensive course is required. When employers come to be better convinced of the benefits resulting, both to man and master, from a servant considering his situation as fixed, and thus being enabled to bring out the capabilities of the grounds intrusted to his charge (which a lifetime is generally short enough to accomplish), it may be more in the gardener's power to know to what branches of education he should most devote his attention. I do not recollect exactly what I said in the Gazette about excretions from roots. I am of opinion, however, that it is most likely the excretions from roots give rise to the fungi found there ; the fungi found there are more likely, as fungi in general, to feed on morbid excreted matter, than on the sound living tissue of the root: the subject, however, is open to discussion. As to the other parts of the essay, it is needless to make repetitions. I take the meaning of the word virgin soil to be, untouched; when pasture has lain long untouched, the soil may get consolidated so far as to regain the property inherent in virgin soil of keeping porous when made so, which no long-worked soil will do. This property, however, is quite independent of any substance contained in the soil; its good effects are more perceptible in light fertile loamy soils than in clayey, but it exists in all new soils ; and, like a layer of charcoal spread on the surface, keeps up the proper communication between the soil and atmosphere, which is indispensable to fertility. It is a physical property belonging to its natural constitution, which gives effect to the mechanical operations of pulverising, which are soon obliterated in effete worn-out soils, by their tendency to dissolve into powder. This is quite independent of any organic matter accumulated in the pasture, or saline substances washed into the subsoil ; it is a natural principle in the constitution of the soil denoting vigour, while long working is productive of an exhaustion which no manures we can apply will altogether remove. The arguments I brought forward on this head in the former essay are what I have considered as solving the question in my own mind, perhaps better than I have been able to explain myself; but I am open to conviction, and may be mistaken, and there is nothing like proper discussion for eliciting the truth. The benefits pointed out by Mr. W. are great, but more in the power of manures to remedy; the other, nothing but time to consolidate, or trench. ing, will amend. I hope, however, that both essays will have been found beneficial as expressions of opinion, on which the readers of the Magazine will form a judgement for themselves. — R. Lymburn. Kilmarnock, November, 1842.
Art. I. Comparative Physiology. By R. LYMBURN.
(Continued from p. 470.) The roots of plants are peculiarly fitted for ramifying in the soil; they are not elongated by expansion like stems, but increase by additions from within to the point, and, not being confined in their developement by joints, ramify wherever they meet with obstructions, or food is found in abundance. They can enter the smallest crevices, and by the additions from within force their way onwards; and, when food is at a distance, the rapidity with which they elongate in quest of it is astonishing: When they meet with porous substances containing absorbed food, they ramify round them in all directions ; and, in rotted leaves or well rotted manure, the fibres are always more abundant than in poor soil. The stomach of plants can only be represented by the soil. As the food of plants requires more decomposition than that of animals, a greater chemical power is found in the soil; and, as plants organise their tissues from nascent elementary substances, much decomposition is required, and the heat of the soil and admission of air cannot be too much attended to. Pitchers and other appendages may assist the general absorbing power, which is found on the whole surface of the plant, especially on the under side of the leaves ; and, in particular circumstances, this general power may take the place of the special absorbing apparatus of root, and may shadow out the possibility of digestive cavities becoming suitable for plants as well as animals. `In as far however as practice is concerned, and for plants under general cultivation, the soil alone can be considered as the stomach; and the necessity of keeping this in proper order becomes at once apparent, and cannot be too much attended to. To keep up a proper degree of heat and moisture in the soil, a certain degree of porosity is required; and when the soil is dug deep in dry weather and
broken small, and when the texture of the soil is such as to preserve that condition for a length of time, the powers of the stomach are such that a much greater effect will be produced, than in adverse circumstances where many times the quantity of food has been deposited. The same quarter of the garden or nursery grounds, especially if the soil is a strong loam inclining to clay, if cropped in separate portions and at different times, will have one part, which was worked dry and got a few dry days after working, producing an excellent crop, while another portion equally well worked and manured, which has unfortunately been subject to saturating rains before the particles of soil were dried sufficiently, will be found much worse. If small seedling crops have been sown there is frequently a total failure; and with stronger crops the growth is weak and yellow, compared with that where, the soil being worked dry and keeping open, the proper action of the stomach is preserved. It is in this way that turf buried, or deposit of roots left from previous crops, acts; or trenching of the soil and bringing up a new surface, which from long lying has recovered its powers of constitution, and is not so apt to run off into powder and close up the pores, as old effete long-worked soil does; it is from these deposits and the renewed constitution of the soil preserving an open porous state, that such astonishing effects are at times produced. I have often seen the crops twice as large from these circumstances alone, and the trees as large in one piece of the same quarter at one year's growth as in another piece at two years' growth, when there was no difference of the manure and other preparations. If the soil is too loose and sandy, or from long working falls into powder too easily, or if it is a strong clay not admitting of breaking freely into pieces, no manure will remedy these defects, unless deposited in such quantities as to alter the texture of the soil; and it is the same with good land, which has unfortunately been battered with heavy rains immediately after pulverisation, especially on clayey loams, which in good seasons and under proper circumstances often produce the best crops. Farm-yard manure acts much in the way of keeping the soil open and absorbing moisture, and this is one of the reasons why it will be found generally superior to concentrated manures, unless where carriage is expensive; by its gradual decay it keeps the soil porous: and concentrated manures will always be found of most value, especially those like guano containing much nitrogen, when mixed up with bulky substances, as sawdust of deciduous wood, peat-moss, scourings of ditches, or refuse of gardens, weeds, &c.
The changes on the substances absorbed by the spongioles of plants are probably confined to the rejection of insoluble substances, changes in the substances taken up being more proper to secretion or assimilation. The absorbents, or especially the absorbing glands, of animals have been thought to produce some changes on the chyle, but this seems uncertain ; and these vessels appear to be endowed with more sensibility than those of plants. The power of endosmose seems similar to that described as hygroscopicity by DeCandolle, but more intimately and fully examined by Dutrochet. It is stated by DeCandolle, Muller, and others, that the connexion of endosmose with electricity, which Dutrochet fancied he had made out, has not been confirmed; it is probable, however, from the connexion of electricity generally with all action, that it will be concerned either as cause or effect. Some have attributed the power to a compound and greater attraction subsisting in a dense fluid from its more compound nature, than in a fluid comparatively more simple; others say that the tissue of the bladder has more attraction for some substances than others, and causes those substances to be longer in passing through the pores. Dr. Carpenter seems to be something of this opinion. Saussure, who made many experiments on this subject, was of opinion that they passed more or less quickly according to their liquidity, which would mechanically allow of their passing the pores more easily. Professor Thomson* objects to this, that more water would require to be absorbed; the quantity of water absorbed by plants under proper circumstances ss, however, so great as to modify this objection; the thinner the fluid it should certainly pass thc more easily, and, if we suppose the operations of nature to be conducted on the most perfect plan, the membrane set apart for absorption should not have that faculty interfered with by another chemical power possessed by the same organ. Vogelf found in his experiments that most plants, if supplied at the roots with an unlimited quantity of saline substances in solution, would absorb so much, even of those found beneficial in smaller quantities, such as nitrate of potash, &c., as to cause death. The sulphate of copper he found, like Saussure, most rapidly absorbed; and this and others partially decomposed, by the abstraction of oxygen reducing the salt to the state of a protosulphate; other saline substances were found unaltered after death, He found that chara and some other plants would not absorb the salts of copper; this he attributes to their containing much carbonate of lime, but it is probably owing to the peculiar formation of the invisible pores, which all absorbing membranes are supposed to possess. Capillary attraction is thought to assist in absorption by furthering the ascent or removal of the imbibed fluid, so as to allow the denser descending sap to renew the phenomena of
endosmose. Some think the fact, that imbibition is sometimes found to have the strongest current from the denser to the lighter fluid, a proof that some other power than endosmose is concerned in imbibition ; others say it is the same phenomenon modified by some peculiarities of the fluids themselves, or of the vessels they circulate in. In animals at least, absorption, if produced by endosmose, must, it is said, be held in check by vitality preventing the mingling of fluids, and causing it to act in some cases and cease in others.
The fact of the existence of an exosmose as well as endosmose current seems to infer the truth of the theory of the excretions by the roots of plants, now generally admitted by most physiologists and chemists, though still doubted by some very eminent men. The experiment of Dr. Madden, in which, having washed the roots of a plant of groundsel, and introduced one half of them into a phial containing water mixed with ulmate of ammonia, and the other half into a phial of pure water, he found at the end of a few days an excretion of a gummy-looking substance in the pure water, seems to confirm and corroborate those of Macaire. The fungi found so abundantly on the roots of some plants, as those of Scotch fir, spruce, oak, &c., must be fed by morbid excreted matter from the roots, probably of a nitrogenous nature, as nitrogen forms so large a proportion of these plants.
Besides capillary attraction and vital contractility, which assist the power of endosmose by furnishing the conditions needed, of removing the thinner imbibed fluid and supplying its place with denser sap, it is thought by many, from the peculiar force with which imbibitions take place in the living spongiole, as compared with the phenomena of endosmose in dead membranes, that a peculiar vital force is also concerned, which may very likely be the case. Besides the absorption by the roots, water and its contents are absorbed by other parts of plants, especially by the under side of the leaf.
(To be continued.)
Art. II. The Principles of Landscape-Gardening and of Landscape
Architecture applied to the Laying out of Public Cemeteries and the Improvement of Churchyards ; including Observations on the Working and General Management of Cemeteries and BurialGrounds. By the CONDUCTOR.
(Continued from p. 494.) IX. Lists or Trees, Shrubs, AND PERENNIAL HERBACEOUS PLANTS,
ADAPTED FOR CEMETERIES AND CHURCHYARDS. In the following selections we have chiefly included plants that are quite hardy, and that, when once properly planted and established, will grow in turf