ON PROP A GA TION Y CUTTINGS. 227 



produced a well-rooted plant. The advantage of propagating by buds 

 or joints is, that a plant is produced from every bud or joint ; whereas, 

 in propagating by cuttings, at least two buds, and commonly several, 

 are required. 



A nodule is a concretion of embryo buds, such as may be frequently 

 seen in the matter extra vasated from the joints of pelargoniums and 

 the stumps of old elms and poplars, olives and mulberries, occasioned 

 by the returning sap not flowing freely to the root. These nodules are 

 seldom used for the purpose of propagation, except in the case of the 

 olive ; but there can be no doubt that they might be employed for this 

 purpose, and would answer, were it not that the plants which produce 

 them are in general very readily propagated by cuttings. The only 

 remarkable instance of propagation by this mode that is on record is 

 practised in Italy with the olive. The old trees are commonly found 

 to contain swellings or nodules in the trunk, called lt uovole," and these 

 being separated, are planted in the soil in the manner of bulbs, and 

 produce plants. 



In propagating by joints of the vine it is reasonable to suppose that 

 the larger the portion of wood attached to the joint the stronger will 

 be the plants produced. Mr. Knight found that the buds of the vine, 

 wholly detached from the alburnum, were incapable of retaining life ; 

 but that a very few grains of alburnum were sufficient to enable a bud 

 to form minute leaves and roots, such as would have been produced by 

 plants raised from seeds. By increasing the quantity of alburnum, the 

 shoots produced from the buds increased in the same proportion ; and 

 when the bud had a piece of two years old wood, a foot long, attached 

 to it, the growth was nearly as strong as it would have been if the bud 

 had remained on the parent tree. In preparing joints of the vine, 

 about half an inch of the wood is left above and below the bud, as in 



fig. 175; but this and all 

 Fig. 175. other plants that are so pro- Fi S- 176 - 



pagated are found to root 



better when the shoot is cut 



through, so as to separate 



about one-third part of the 

 A joint of a vine pre- pith, as shown in fig. 17 Q. A joint of a vine, in which 

 pared in the com- B th j j ^ mode f treat _ two-thirds of the shoot 

 mon manner, and J . , and pith are removed 



planted. ment P lants have been raised previous to planting. 



from buds and half-joints of 

 camellia, poinsettia, euphorbia, brugmansia, and other species. 



Propagation by bulbs, and entire tubers and tubercles, is effected 

 simply by separating them from the parent plant, and inserting them 

 in the soil about the same depth at which they are found on the parent 

 plant, or a little deeper in very light soil, and not quite so deep if in 

 very heavy soil. A. phenomenon, De Candolle observes, common to all 

 tubers is this : that while in the seed the radicle or descending part 

 pushes first, in the tuber, on the contrary, the ascending part or 

 plumule is first developed, and the roots appear a short time after- 

 wards. 



