444 REPRODUCTION. 



1138. The new individual, for instance a bud, arising from 

 non-sexual reproduction, generally repeats in itself all the pecu- 

 liarities of the organism from which it took its origin ; the new 

 individual, the seed or spore, arising from sexual reproduction, 

 usually differs in some particulars from the organism or organ- 

 isms by which it was produced. 



1139. Hence, in the higher plants individual peculiarities are 

 perpetuable by bud- reproduction, whereas the seed gives rise to 

 variations. If the horticulturist wishes to keep the descendants 

 of a given stock true to all the characters which give them value, 

 he relies upon some method of multiplying the plant b}* buds ; 

 if, on the contrary, he desires to induce or increase some varia- 

 tion from the stock, he makes use of seeds. 



1140. The ordinary horticultural operations by which buds are 

 severed from the parent stock and suitably placed for further 

 advantageous development are : (1) layering, the fastening a 

 branch in earth, so that while yet connected with its main stem 

 it may form new roots and afterwards live independently of 

 the stem ; (2) the forcing of cuttings or slips, which in con- 

 genial soil will produce a supply of roots ; (3) grafting, or the 

 transfer of a shoot (a scion) from the parent plant to some other 

 plant by which it can be nourished ; (4) budding, the transfer of 

 a single bud to another plant (see 426). 



1141. While in most cases buds produce shoots or plants very 

 closely resembling the parent, it sometimes happens that re- 

 markable variations arise. These are known as bud-variations, 

 and are commonly called sports. In general, when once origi- 

 nated they are perpetuable by any of the processes of bud- 

 propagation just described, but are not likely to be reproduced 

 by seed. From the long list of them given by Darwin only a 

 few familiar cases are here mentioned: (1) the moss-rose, from 

 the Provence rose (Rosa ceutifolia) ; (2) Pelargonium, giving 

 rise to numerous varieties ; (3) Dianthus, Sweet William, Car- 

 nations, and Pinks, which vary very widely in cuttings from 

 a single plant. 



1142. Many of the cases of sports, especially those which have 

 descended from hybrids, are attributable to reversion to an ances- 

 tral form ; a few seem to be dependent on changes in the sur- 

 roundings ; while others have been attributed to the influence 

 exerted by a graft. 



1143. Ordinarily the scion produces no marked effect upon the 

 stock, and, conversely, the stock exerts no effect upon the shoot 

 growing from the scion. But when, for instance, some of the 



