Transactions of the London Horticultural Society. 473 



themselves, and they can at any time be taken out of the pots without the 

 least danger of their losing any part of their roots or mould. 



" In the management of my melon plants, T have during several past years 

 adopted a mode of treatment which I have found very highly beneficial ; and 

 which I shall take this opportunity of describing and recommending. I use 

 pots of about 5 in. wide and as many deep, but without any bottom. These 

 are put to stand upon a piece of tile or slate, and are lined with hay in the 

 manner above mentioned, the plants being always put into them as soon as 

 the seed leaves have become unfolded. When the plants are transferred to 

 the hotbed, the piece of tile or slate is taken away, and the pot is immersed 

 to half its depth in the soil. Water is given to the mould in the pot, till the 

 roots of the plant have extended themselves in the mould of the bed, but not 

 afterwards ; and the base of the stem in consequence not being ever wetted, 

 never cankers, or becomes diseased." 



34. On the Propagation of Trees by Cuttings in Simmer. By T. A. Knight, Esq., 

 F.R.S., Pres, Read April 3. 1838. 



'^ When a cutting of any deciduous tree is planted in autumn, or winter, or 

 spring, it contains within it a portion of the true, as it has been called, or 

 vital sap of the tree of which it once formed a part. This fluid, relatively to 

 plants, is very closely analogous to the arterial blood of animals; and I shall 

 therefore, to distinguish it from the watery fluid, which rises abundantly 

 through the alburnum, call it the arterial sap of the tree. Cuttings of some spe- 

 cies of trees very freely emit roots and leaves ; whilst others usually produce a 

 few leaves only, and then die ; and others scarcely exhibit any signs of life : 

 but no cutting ever possesses the power of regenerating, and adding to itself 

 vitally, a single particle of matter, till it has acquired mature and efficient 

 foliage. A part of the arterial sap previously in the cutting assumes an or- 

 ganic solid form ; and the cutting in consequence necessarily becomes, to 

 some extent, exhausted. 



" Summer cuttings possess the advantage of having mature and efficient fo- 

 liage, but such foliage is easily injured or destroyed, and if it be not carefully 

 and skilfully managed, it dies. These cuttings (such as I have usually seen 

 employed) have some mature and efficient foliage and other foliage, which is 

 young and growing, and consequently two distinct processes are going on at 

 the same time within them, which operate in opposition to each other. By 

 the mature leaves, carbon, under the influence of light, is taken up from the 

 surrounding atmosphere, and arterial sap is generated. The young and im- 

 mature leaves, on the contrary, vitiate the air in which they grow by throwing 

 off carbon ; and they expend, in adding to their own bulk, that which ought 

 to be expended in the creation of shoots. This circumstance respecting the 

 different operations of immature and mature leaves upon the surrounding air, 

 presented itself to the early labourers in pneumatic chemistry. Dr. Priestly 

 noticed the discharge of oxygen gas, or dephlogisticated air (as it was then 

 called), from mature leaves ; Scheele, making, as he supposed, a similar ex- 

 periment upon the young leaves of germinating beans, found these to vitiate 

 air in which they grew. These results were then supposed to be widely at 

 variance with each other ; but subsequent experience has proved both philoso- 

 phers to have been equally correct. 



" I possess many young seedling trees of the Ulmus campestris, or suberosa, 

 or glabra, for the widely varying characters of my seedling trees satisfy me 

 that these three supposed species are varieties only of a single species. One 

 of these seedling plants presented a form of growth, which induced me to 

 wish to propagate from it. It shows a strong disposition to aspire to a very 

 great height with a single straight stem, and with only very small lateral 

 branches, and to be therefore calculated to afford sound timber of great length 

 and bulk, which is peculiarly valuable, and difficult to be obtained, for the 



1840. Sept. I i 



