GENERAL PUliX'IS CUNClCI'tNlNC FRUIT TREE STOCKS 



rf-'i 



ilivcrsu as the varieties tlieinsclvcs ; Red Astrachan, fur instance, 

 lias an cxcefflin,t;]y liljrous r(jot system with few tap roots, while 

 (JUlcnbnrf,' and Fanieusc grown on either side of the Red Astrachan 

 riiw, are almost destitute of root rd)ers, having instead deep tap roots 

 wiih two or three prongs. Nurserymen declare the weaker the 

 top growth and the sparser the foliage of a variety, the more 

 del'.cient is the root growth. 



228. Plant cliimeras or "graft-hybrids." — To the general rule that 

 slock and cion retain their identity there is a seeming exception in 

 the pseudo-hybrids or plant chimeras of experimenters. When, after 

 grafting, cion buds fail to grow and an adventitious bud arises at 

 the junction of stock and cion, including cells from both parts, we 

 have what for many years was known as a graft-hybrid, but is 

 now more accurately called a plant' 

 chimera. In a case of this kind the 

 cells from stock and cion reproduce 

 themselves, sometimes the wood of one 

 covering the other like a glove, or it 

 may be the wood of the consorting 

 pair grows side by side in parallel parts 

 throughout the plant. These plant 

 chimeras are more or less familiar in 

 apples half sweet, the other half sour; 

 or in which a portion of the apple is 

 red or yellow and another russet. They 

 are probably more often found in citrus 

 fruits than in any others. It is pos- 

 sible that the cells of two consorting 

 parts do actually blend in some cases, 

 forming a true hybrid. Not improbably 

 some of the many so-called strains of fruit described by those 

 seeking to improve plants by bud selection are plant chimeras. 



229. Explanations for reciprocal effects. — Plant physiology does 

 not help us much in elucidating the inHuence of grafting. The- 

 oretically, from the anatomy of plants, we can expect nothing more 

 in grafting than the adhesion of graft to stock. The tissues below 

 the union are those of the stock; above it, those of the cion. Yet 

 there is some reason to suspect that definite substances pass from 

 one to the other in the consorting parts of a grafted plant and 

 produce specific effects. Thus, when a cion with variegated 

 foliage is grafted on a normal stock, shoots which spring from the 

 stock below the graft are variegated. Or, if deadly nightshade be 

 grafted on tomato, the poison, atropine, passes down into tomato 

 root and stem. But curiously enough, if the variegated plant or 

 the nightshade be used as a stock, variegation in one case and 

 atropine in the other do not pass upward into the cions. 



An ingenious and not at all improbable reason for some of the 

 influence of the stock upon the cion was offered in the French 

 Academy of Science [by Le Clerc du Sablon]. The speaker had 



FIG. 154 — TRANSPLANT- 

 ING IN LOOSE SOIL 



