14th, there was no alteration in the stumps, the sap reached nearly to the ground, and the upper wounds were encrusted over with a nasty fetid mucilage. During the above eight days, the weather was fine with a good deal of sun. Medium of heat 61°, and of cold 40°. In the night before the 15th, the weather changed to a sharp cutting wind, and the sap ceased to flow from any of the most recent wounds. No alteration in the stumps or trees till the evening of the 20th except a very slight exudation from the trunks of recently felled trees, which, when wiped off, appeared to come from all parts of the wood, medulla, and alburnum alike. Medium of heat those six days 52°, of cold 41°. On the 21st and 22d, a little sap exuded from the most recent wounds and felled trees, which was quite thick and glutinous. Those two days were fine, with 64° and 66° of heat. At this time, the strong roots would exude just sufficient to moisten dry earth dusted on a recent wound; and the extreme ends of the fibrous roots looked white, just as if they were beginning to grow. On the 23d, heavy rain and cold set in, and continued to the 30th; during which time I could not find the least change in the young shoots, which stood at one, two, or three young leaf joints, and about as many inches long, or did the roots advance, no sap exuded from roots or branches. The medium of heat in the last ten days was 50,0, and of cold 42 and 33 in. of rain had fallen. 10 2 The observations were continued to the 4th of May, on which day, all the standing trees, and stumps of the felled trees, clearly denoted an extension of young wood and roots, and a mucilaginous matter rested on the surface of all the stumps with minute globules of air in and under it. Whether the air was from the combined effects of rain, sap, and heat, or came from the root stumps I could not distinguish. the last four days, 10% of an inch of rain had fallen in genial showers; and the medium of heat was 62°, and of cold 46°. In This terminated these experiments; but others had been made with exactly the same results as to the primary motion of the sap, and progress of vegetation: but, with regard to time, there was a material difference; viz. a vine in a pot put into a pine stove, on the 13th of March, completed the process in eight days, and a small birch tree in a pot, put in the same situation on the 5th of April, got through the same process in rather less than five days. Welbeck, Feb. 1. 1826. Yours, &c. JOSEPH THOMPSON. ART. V. An Essay on Physiological Botany, in Continuation of the Experiments described in the preceding Paper. By Mr. JOSEPH THOMPSON. Sir, AFTER four years more of extensive practice, and close attention to the ordinances of nature in this branch of my profession, I am satisfied that the present theoretical system of vegetable phenomena was founded in error by Malpighi and Grew. Had they commenced their experiments earlier in the season, and wounded the extremities of the branches, they would have obtained pure limpid sap many days before they got it in the cylindrical wimble holes, in which they never could discover from what part of the cylinder it was produced, the accumulation would only appear in the lower segment of the cylinder, which naturally led to the supposition that it was propelled upwards. The late Sir James Edward Smith, in his Introduction to Physiological and Systematic Botany, has brought into view most of the experiments made on this subject, from the time of Malpighi down to those of Thomas Andrew Knight, Esq., whose experiments on the cuttings of fig trees are recorded in the Transactions of the Philosophical Society of 1801, 1803, and 1804. The Rev. Mr. Keith has also collected all that has been written on this subject. The experiments conducted and related by those very scientific persons do not, however, appear to me satisfactorily to establish the conclusions that have been drawn from them, and I now proceed to add to my former observations on this subject a statement of facts which seem to impugn their solidity. Sir J. E. Smith, in his book above quoted, says, "much contrariety of opinion exists on the vascular system of plants, propulsion of sap, &c." The excellent plates of Anthony Tod Thomson, in his Lectures on Botany, show that the anatomy of plants and the vascular system are correctly understood; but the propulsion of sap, its change to cambium and deposit in wood, the time occupied, and temperature most congenial to those operations in the vegetable system, are clouded in darkness. The following quotations will show that some writers have accidentally hit upon the true system, in so far as regards the primary motion of the sap. In Miller's Gardener's Dictionary, second edition, printed in .1741, under the article Pérsicum (Peach), he says: "It sometimes happens that the roots are buried too deeply; for the sap which is contained in the branches being put strongly in VOL. V. No. 20. motion by the warmth of the sun early in spring, its strength is lost before the sun can reach its roots to put them in equal motion, which causes the blossoms to drop off and the shoots to become stagnant." The above quotation is susceptible of strong comments, but I proceed to notice Mr. G. Bliss's Practical Treatise on the Cultivation of Fruit Trees (1825). At page 60., on Grafting, he denies any influence of the stock on the scion engrafted thereon, and says, "the fund of vegetable matter above ground must be filtered through the roots," &c.; and that "the stock partakes of the nature of the scion; for there cannot be an existing doubt but that the roots, veins, fibres, or whatever they may be called, strike from the scion into the stock, and run downwards to the extremity where the sap flows." He then gives an instance of a variegated jasmine being budded on a common green one, and several of the buds below the one inserted became variegated. Mitchel in his Dendrològia, published in 1827, denies the circulation of sap, and designates the branches, fronds, buds, and leaves, as caterers to the tree. Van Helmont's experiments on the willow tree, which increased 119 pounds in five years, and only wasted 3 ounces of earth, show that the sap to sustain the tree, with its increase of 119 pounds, could not be derived from the earth, or else a greater waste must have taken place. Or must all that increase be attributed to the distilled water he gave it? I now offer some instances of practical operations occurring yearly in the plashing of quickset hedges, which is done by the common labourer, who cuts out all such shoots as are not wanted for the layers; the latter he cuts nearly off, leaving no more than a bit of bark, and a small thin portion of wood on one side, the substance of which, in the case of a strong layer, is not more than a common leather strap; the thinner it is, the better for the layer. Here we see the epidermis, cortical body, liber, wood, corona, and pith, all severed, and, in some cases, part of the stump or stock cut off, leaving 4 to 8 in. space between the body of the stool and layer. Yet we see the layers in a full healthy state of vegetation, with an exudation of sap from the lower end, many days before the gaseous atmospheric influence acts upon the stock or stump. In this case I do not see that it is probable, and scarcely possible, that the ramifications of the layer, to the extent of 10 or 15 ft., could be fed and supported by the small, strap-like, connecting splice at the bottom. The most superficial observer must have seen moderatesized elm trees vegetate strongly the first, and weakly the se→ cond, year, after they are felled and laid by without either root, but, or top branches. In the spring of 1826, I noted a knotty arm or branch of Pseudacàcia (Cobbett's Locust Tree), about 12 ft. long and 10 in. in diameter, accidentally thrown across other pieces of wood, under the shade of a yew tree, and in a damp situation, but supported at least one foot from the earth. Most of the burry knots vegetated more or less; one shoot attained a length of 15 in.; in the following winter the upper end of this shoot perished, but, in the spring of 1827, the remainder vegetated, and produced the length of 9 in. more of young wood; and vegetation also took place on every knot, to within about 2 ft. of each extremity of the piece or arm. I was informed by an intelligent and sensible woodman (the late Mr. Yates), that he saw a willow, or sallow, pole, pointed at both ends, and put into the middle mortices of two threeholed posts in the gap of a hedge, under the shade of some sallow trees, in a moist situation by the side of a rivulet, which vegetated two years. All men who fell and peel oak timber will verify the fact, that the tree will peel earlier in the peeling season, and easier at top than bottom. In the striking of hard-wooded heaths, and other choice botanical cuttings, as well as those of the gooseberry and all the tribe of Sálices, we are sure that nothing can be derived from the earth at the outset of the operation, the power of vegetation must be contained in the cutting, and that sufficiently to create its own roots and perfect the rooted shrub or tree. It is found in practice that a vine cutting, planted ever so much, say a foot, below the surface, will only make roots at that bud nearest the surface; and a single bud, cut off a shoot with a small portion of bark and wood, not larger than a horse bean, will produce as good a plant as a cutting a yard long. I offer one more practical proof of the descent of the sap, which demonstrates that every bud of a tree contains the same latent vitality as that contained in the seed sperm. But the means of preserving the vegetating powers of the cuttings and buds is very limited. Oranges have been grafted in almost every month of the year, and pinks and carnations, and other herbs, may be propagated by cuttings in all the spring and summer months. The proof I offer is in the grafting of vines out of season. In the last two years I took cuttings for grafts off the latest vines; those I preserved in a temperate cellar, until the fruit of the earliest forced vines was all gathered, the leaves fallen off, and the vine wood as dry and torpid as an oak tree in January. I then inserted the scions by vertical incisions, leaving the tops of the vines entire; the inserted grafts soon vegetated, and became lateral branches, and were the only parts of the vines which showed the least signs of life, for months after their insertion. If those grafts derived the vegetating power from the stock of the old vines, it is an unaccountable circumstance that no other part of the vines vegetated before the approach of the next forcing season. This fact alone is quite sufficient to show that the present notions on this branch of the botanical system are incorrect and erroneous. Yours. &c. Welbeck, April, 1829. JOSEPH THOMPSON. ART. VI. Sir, Further Improvements in the Mode of heating Hothouses by hot Water. By ROBERT BYERS, Esq. SINCE I had the pleasure of addressing you, on the hotwater system, many improvements have occurred to me, arising from various causes, the principal one, that of having my small houses and pits to remove to this place, and to re-erect; also, from the numerous communications which I have received in consequence of my letter to you. As space in your Magazine is valuable, I will not explain how, or why, these plans occurred to me, but at once attempt to detail them, first giving what I consider the proper powers of a hot-water apparatus, and, without these powers, it does not appear to me that it can fully answer the purposes of the horticulturist with certainty: 1. It should have the means of producing rather more heat than may be required; 2. of applying that heat at pleasure, and in a very short time; and 3. of retarding that heat when necessary. These properties are certainly to be obtained by the use of water, and, as a general guide, every apparatus should, when in full work, have the power of raising the temperature of the house, frame, or pit, from 45° to 55°, or even 60°; granting it has this power, and the thermometer sinks to 20° out of doors, the temperature in your house will be 65° to 80°, which I conclude sufficient for all winter forcing. For some time I have been anxious to determine the exact quantity of heat given out by each foot of pipe of a given size, at a certain temperature; or, in other words, how many cubic feet of air can be raised to a required temperature by a given quantity of water, say at 120° of heat. Perhaps some of your mathematical readers may be induced to make the experiment |