204 PROPAGATION. 



The process by which a shoot or part of a shoot, 

 a single hud, or even, in some cases, a single leaf, 

 becomes an independent plant, is owing to the con- 

 stitutional powers of the vital envelope of the system. 

 This member, as has been before observed, possesses 

 the faculty of protruding its lower part downward, or 

 ejecting slender portions thereof into the ground, 

 having all the members and powers of those roots which 

 are produced from the corculum of a seed. The first 

 roots produced by a seed proceed from that part of 

 it called the rostellum, but how radicles are generated 

 from the bottom of a cutting is not so easily conjec- 

 tured. They issue from the vital membrane, but in 

 what manner it is difficult to describe. 



The proper depth at which cuttings should be put 

 in cannot always be strictly attended to. Exotic 

 cuttings, raised under the protection of glass, may, 

 and commonly are, put no deeper into the soil 

 than is suitable, that is just within the surface ; but 

 those of hardy plants are generally, for the sake of 

 security, let in deeper than the ready striking of the 

 cuttings require. It is worthy of remark, that the 

 same distance below the surface which is so suitable 

 for the healthy germination of seed, is also the most 

 favourable for the ejection of the roots of cuttings. 

 It seems that a certain modified influence of the 

 atmosphere is necessary in both processes. Cuttings 

 of gooseberries, common laurel, &c., when taken up 

 after they are struck, appear rooted as Fig. 51, 



