388 



SCIENCE OF GARDENING. 



PART II. 



up, and the earth shaken from its roots ; the whole is then separated, each piece containing 

 a portion of root and stem, which may be planted without farther preparation. 



1991. By runners (Jtg> 376. c). With certain species this is a very convenient and 

 sure mode of propagation. All that is requisite, is to allow the plantlet on the shoot or 

 runner to be well rooted before being separated from the parent. It may then be planted 

 where it is finally to remain. 



1992. By suckers. (Jig. 376. 6). These are merely runners under ground ; some run 

 to a considerable distance, as the acacia, narrow-leaved elm, sea-limegrass, alkekengi, 

 &c. ; others are more limited in their migrations, as the lilac, syringa, Jerusalem arti- 

 choke, saponaria, &c. All that is necessary is to dig them up, cut off each plantlet with 

 a portion of root, after which its top may be reduced by cutting off' from one fourth to 

 one half of the shoot, in order to fit it to the curtailed root, and it may then be planted, 

 either in the nursing-department, or, if a strong plant, where it is finally to remain. 



SUBSECT. 2. Projxigation by Layering. 



1993. Layers, as we have already observed (840.) are indicated by nature, and we 

 shall here point out the improvements of art and their applications. The roots in natural 

 layers are produced by the stimulus of the moist earth on which the shoots, from the na- 

 ture of the tree or plant, or accidental causes, recline ; art increases the natural stimuli, 

 and adds others, especially that of diminishing the resources of the shoot in the parent 

 plant, by incision or fracture. 



1994. Season. In general, the operation of layering in trees and shrubs is commenced 

 before the ascent of the sap, or delayed till the sap is fully up, and thence the two seasons 

 are early in spring or in midsummer. Autumn and winter are resorted to for convenience 

 in extensive concerns. The shoot, or extremity of the shoot, intended to become a new 

 plant, is half separated from the parent plant, at a few inches' distance from its extremity, 

 and while this permits the ascent of the sap at the season of its rising,. the remaining half 

 of the stem being cut through and separated, forms a dam or sluice to the descending 

 sap, which, thus interrupted in its progress, exudes at the wound in the form of a gra- 

 nulous protuberance, which throws out roots. If the cut or notch in the stem does not 

 penetrate at least half way through, some sorts of trees will not form a nucleus the first 

 season ; on the other hand, if the notch be cut nearly through the shoot, a sufficiency of 

 alburnum or soft wood is not left for the ascent of the sap, and the shoot dies. In deli- 

 cate sorts it is not sufficient to cut a notch merely, because in that case, the descending 

 sap, instead of throwing out granulated matter in the upper side of the wound, would 

 descend by the entire side of the shoot ; therefore, besides a notch formed by cutting out 

 a portion of bark and wood, the notched side is slit up at least one inch, separating it by 

 a bit of twig, or small splinter of stone or potsherd. 



1995. Manipulation. Shoots when layered are often cut and mangled at random 

 ( t fig. 377. a, b, c), or buried insufficiently, or so deep in the soil (d) that they throw out 

 but few roots ; or not placed upright (e) , by which they make unsightly plants. In order 

 to give some sort of principle to go upon, it should be remembered, that the use of the notch 

 is to prevent the heel or part intended to throw out granulous matter from being bruised, 

 which it generally is, by the common practice of performing this operation by one cut 

 sloping upwards; and that the use of the slit is to render it more difficult for the 



377 



descending sap to return from the extremity of the heel. In conformity with this idea, 

 Knight recommends taking up the shoot after it has grown some time, and cutting 

 off a ring of bark below the notch and slit, so as completely to hinder the return of the 

 sap, and thereby force the shoot to employ it in forming roots. (Hort. Trans, vol. i. 256.) 

 In burying an entire shoot (/) with a view to induce shoots to rise from every bud, 

 notches alone are sufficient without either slitting or ringing. The use of the splinter of 

 wood, or bit of tile or potsherd, is partly to prevent the union of the parts when the bent 

 position of the shoot is not sufficient, and partly, and in some cases principally, to act as 

 a stimulus, like the bottom and sides of pots. - On what principle it acts as a stimulus 



