PROPAGATION BY LEAVES. 271 



618. To induce stems or shoots to produce leaves or growths from which cut- 

 tings may be formed, various modes have been adopted, the object of all of 

 which is to stimulate the normal or latent buds. The most common mode 

 with plants in pots or under glass, is by an increase of temperature and atmo- 

 spheric moisture ; but there are modes which are applicable to all plants 

 whatever, the object of which is to interrupt the ascending or descending 

 sap. When the ascending sap is accumulated by art at a joint, and can no 

 longer pass freely onwards, it stimulates the buds which exist there, either 

 normal or adventitious, to develop themselves, and the sap thus escapes 

 organised into the form of leaves or shoots ; while the interruption of the 

 descending sap, more especially under a joint or bud, produces an accumu- 

 lation or callosity there, which, sooner or later, is organised into roots. To 

 accumulate the ascending sap at any point, the shoot maybe bent to one side 

 from that point ; and it may be bent back again from a second point, and if 

 the shoot is long, the operation may be repeated, so as to leave it in a ser- 

 pentine or zigzag form from every exterior angle in 

 y_ which, as at a, a, in fig. 182, a bud will be developed. 



Where the shoot cannot conveniently be bent, a notch 

 may be made in it immediately above a bud, so deep 

 as to penetrate the alburnum ; or in the case of more 

 slender shoots, the knife may be merely inserted 

 above the bud, or above several buds, so as to penetrate 

 into the alburnum, and the wound kept open by insert- 

 ing wedges in them, as in fig. 180, a. Some days or 

 weeks afterwards, according to the nature of the plant, 

 a notch or cut may be made under the bud, in order 

 a to interrupt the sap returned by the leaf, and thus 



^__ form a callosity there for the production of roots. In 



Fig. 182. A shoot bent to cause^* wav a11 tne DU(Js or joints on a tree or shrub of 



the buds at the angles to pro. almost any size maybe prepared; and if a tree so 



treated could be covered with moss kept moist, leaving 



only the buds, or the joints, or points from which buds were expected, exposed 

 to the light ; or if it could be laid down on the surface of soil kept moist, and 

 very slightly covered with soil, or laid down flat on the surface of water, so 

 as just to touch it, a rooted plant, or at least a shoot, would be produced 

 from every bud or joint. In preparing buds in this manner, however, it 

 must always be borne in mind, either that the plants require to be kept in a 

 close, moist atmosphere, or to have the wounds covered with moss or soil ; 

 for if they are exposed to dry air, they will frequently neither cicatrise, nor 

 emit roots, in consequence of the excessive evaporation which will necessarily 

 take place. 



Even the petioles of large leaves may be prepared before they are taken 

 off, by being cut half through near the base, by which means they will form 

 a callosity there, and root more rapidly when planted. The roots of plants 

 which contain latent buds may be stimulated to develop them by the ex- 

 posure of portions of them to the light, or by bending, or twisting, or cutting 

 notches in them, in the same manner as in stems. Piercing the stems or 

 roots by a longitudinal cut through a joint, and keeping the wound open with 

 a wedge or splinter, or driving pegs or nails through them, will facilitate 

 both the formation of roots and the development of buds ; and various other 

 modes of exciting buds, and causing the protrusion of roots, will occur to the 



T 2 



