THE LIFE -HISTORY OF PLANTS. 



13 



Juidperus Virginiana. Another frequent change is 

 a change of habit. By grafting an Apple on a 

 dwarfing stock, like the Paradise, or the Pear on the 

 Quince, a giant is, as it were, converted into a pigmy, 

 and the fruitfulness is not only greatly increased, but 

 much hastened, so that the old proverb that " he who 

 plants Pears, plants for his heirs," is no longer wholly 

 true. 



In " double grafting," again, the effect of stock on 

 scion is shown. In some cases the Pear will not 

 graft readily on the Quince, and the advantages of 

 such a graft would consequently not be available 

 were it not for this process of double grafting. This 

 is effected by first of all grafting a scion of some 

 other Pear on to the Quince stock, and then graft- 

 ing on to this first scion the particular Pear it 

 is wished to propagate. In this indirect manner 



character of the fruit, it is difficult to see why 

 changes in the form of the fruit should not occur 

 likewise. Those who deny this say that the inter- 

 mediate forms, which undoubtedly do occur, are 

 instances of variation not greater in amount than 



Fig. 55.— Shoots prepared for graftiug by approacli 

 or it-arching. 



the Quince stock is made to affect the second 

 scion through the first, and to hasten and increase 

 its fruitfulness. 



Influence of the Scion on the Stock. — The 



eifect of scion on stock is perhaps less conspicuous, but 

 occasionally becomes very manifest, as where a shoot 

 of the same character as the scion breaks out from the 

 sides of the stock below the original graft. Such 

 cases are not infrequent, and prove the reciprocal in- 

 fluence of scion and stock. Sometimes even inter- 

 mediate forms of fruit or of foliage are produced, 

 which suggest a commingling of elements, as in 

 cross-fertilisation or hybridisation. If stocks induce 

 dwarfing, promote early flowering, or in other cases 

 retard it, if they alter the flavour and general 



Fig. 56— In-arching : the stem of the plant in the pot is in- 

 arched on to the stem of the plant growing in the 

 ground ; and wlien union is established between them, 

 the stem of the plant in the pot will be cut across below 

 the ligature. 



such as are known to occur naturally without graft- 

 ing. The difficulty of explaining these cases was 

 greater when it was believed that each cell of which 

 plants are built up was a closed bag independent of 

 its neighbours, fluids only passing from cell to cell 

 by exudation and osmosis ; but improved methods 

 of research and more delicate observations have 

 proved the passage in so many instances of very 

 fine threads of protoplasm from one ceU to another, 

 that " continuity of protoplasm" may be considered 

 a general occurrence in the younger tissues where 

 growth and physiological activity are most intense. 

 Assuming its general occurrence in the younger- 

 growing tissues of plants, as we have every reason to 

 do, the explanation of some of the effects of grafting 

 and of " sports or bud variations," wherein from a 



