334 METAMORPHOSIS 



grafting the scion has the form of a disk of cortex subtending a bud, carefully 

 separated from the wood, and which is squeezed into the stock, close against 

 the cambium, after the lifting up of two flaps of cortex. The cambium of the 

 scion unites with the cambium of the stock and thereafter the bud develops. 

 Of the numerous methods of budding we need select only one, viz. budding by 

 clef ting. The end of the stock is split longitudinally and the wedge-shaped base 

 of the scion is sunk in the cleft. In this, as in the previous case, a good junction 

 must be obtained if a fusion is to result. 



We may, as we have already seen, transplant the scion on to another species, 

 still it is impossible to graft any plant on another, for a certain degree of relation- 

 ship between scion and stock is requisite, although the capacity for amalgamation 

 runs by no means parallel with systematic relationship. Apples and pears, 

 for example, graft badly on each other, although they belong to the same 

 genus, while pears graft very readily on the quince, which is placed in another 

 genus. Similarly potatoes graft more readily on Datura and Physalis than on 

 many species of Solanum. We are able apparently to graft easily all other 

 species of Cactaceae on Peireskia aculeata, while other species of Peireskia 

 graft badly on this species. We must take cognisance of all these facts, al- 

 though we may not be able to explain them. The point of interest for us, how- 

 ever, in these cases of transplantation lies in the numerous correlations which 

 we may eludicate by their means. The interrelations between two species 

 thus fused together must operate in the same way as between two parts of one 

 plant since the union is a complete one, for STRASBURGER (1901) was able to 

 prove a fusion of the protoplasm of the stock and scion. 



The interactions which take place between scion and stock may be shown 

 in the first place to be purely quantitative. There are plants which develop 

 better as scions on other species than on the same species, e.g. Physalis 

 on Solanum, Arabis albida on Brassica oleracea, Solanum dulcamara on 

 Lycopersicum. On the other hand, the development of the scion may be 

 retarded by the stock, and since retardation of vegetative growth is usually 

 accompanied by increase in flower-formation, grafting is for this reason fre- 

 quently resorted to in fruit-tree culture. Pears, for instance, which it is 

 desired to cultivate as dwarfs, are grafted on the quince, and apples on Malus 

 Paradisiaca with the same object. Changes in mode of growth are often 

 accompanied by a change in the duration of life, thus dwarf apple-trees, 

 grafted on Malus paradisiaca grow only for fifteen to twenty-five years, while an 

 ordinary apple-tree may attain an age of about 200 years. Pistacia vera, grown 

 from a seedling, will live for 150 years, but if grafted on Pistacia terebinthus, 

 for 200 years, if grafted on Pistacia lentiscus, for forty years only ; in the one 

 case, therefore, the duration of its life is increased, in the other reduced. Annual 

 plants cannot, as a rule, be made perennial by grafting, but LINDEMUTH (1901) 

 has found that the annual Modiola caroliniana lived for 3 \ years when Abutilon 

 thompsoni was grafted on it, and similar results in other cases are extremely 

 probable. 



If we turn now to the special qualitative effect we must note first of all 

 that as a rule (compare Lect. XXIX, p. 381) this effect does not go so far as to 

 cause a modification of the specific characters of the two united plants, and 

 on this knowledge rests the employment of the process of grafting in horticultural 

 practice. There are other qualitative changes, however, which make their ap- 

 pearance, e.g. fruit-trees maybe made, by grafting, to produce an increased yield 

 of flowers and fruit. To VOCHTING (1892) we owe a very interesting experiment 

 on the qualitative effect of grafting. He showed that large-leaved shoots arise 

 from the buds which spring from the base of the inflorescence of the beet in the 

 second year if they be grafted on a one-year-old stock, inflorescences if on a two- 

 year-old stock. These buds if left in their natural positions would, of course, 

 have disappeared in autumn, but when transplanted they are stimulated to 



