138 CUTTINGS. 



XIII. Cuttings. 



311. When a separate portion of a plant is caused to produce new roots 

 and branches, and to increase an individual, it is a cutting. 



312. Cuttings are of two sorts: cuttings properly so called, and eyes 

 (319). 



313. A cutting consists of an internodia, or a part of one, with its 

 nodi j59; and leaf-bud. 



314. When the internodia is plunged in the earth it attracts fluid from 

 the soil, and nourishes the bud until it can feed itself. 



315. The bud, feeding at first, upon the matter in the internodia, grad- 

 ually enlongates upward into a branch, and sends organized matter down- 

 ward, which becomes roots. 



316. As soon as it has established a communication with the soil, it be- 

 comes a new individual, exactly like that from which it was taken. 



317. As it is the action of the leaf-buds that causes growth in a cutting, 

 it follows that no cutting without a leaf-bud will grow ; 



318. Unless the cutting has great vitality and power of forming adven- 

 titous leaf-buds (119), which sometimes happens. 



319. An eye is a leaf- bud without an internodia. 



320. It only differs from a cutting in having no reservoir of food on 

 which to exist, and in emitting its roots immediately from the base of the 

 leaf-bud into the soil. 



321. As cuttings will very often, if not always, develope leaves before 

 any powerful connection is formed between them and the soil, they are 

 peculiarly liable to suffer from perspiration. 



322. Hence the importance of maintaining their atmosphere in an uni- 

 form state of humidity, as is effected by putting bell or other glasses over 

 them. 



323. In this case, however, it is necessary that if air-tight covers are 

 employed, such as bell-glasses, they should be from time to time removed 

 and replaced, for the sake of getting rid of excessive humidity. 



324. Layers differ from cuttings in nothing except that they strike root 

 into the soil while yet adhering to the parent plant. 



325. Whatever is true of cuttings is true of layers, except that the latter 

 are net iiable to suffer by evaporation, because of their communication with 

 the parent plant. 



326. As cuttings strike roots into the earth by the action of leaves or leaf- 

 buds, it might be supposed that they will strike most readily when the 

 leaves or leaf- buds are in their greatest vigour. 



327. Nevertheless, this power is controlled so much by the peculiar vital 

 powers of different species, and by secondary considerations, that it is im- 

 possible to say that this is an absolute rule. 



328. Thus Dahlias and other herbaceous plants will strike root freely 

 when cuttings are very young ; and Heaths, Azaleas, and other hard-wooded 

 plants, only when the wood has just begun to harden. 



329. The former is, probably, owing to some specific vital excitability, 

 the force of which we cannot appreciate ; the latter either to a kind of 

 torpor, which seems to seize such plants when the tissue is once emptied 

 of fluid, or to a natural slowness to send downward woody matter, whether 

 for wood or not, which is the real cause of their wood being harder. 



12* 



