273 DEFINITE ACTION OF THE Chap. XXIII. 



varied less than any other domesticated bird, except tho 

 peacock. 



Bud-variation is, also, important under our present point of 

 view. In some few cases, as when all the eyes on the same 

 tuber of the potato, or all the fruit on the same plum-tree, or 

 all the flowers on the same plant, have suddenly varied in the 

 hame manner, it might be argued that the variation had been 

 definitely caused by some change in the conditions to which 

 the plants had been exposed; yet, in other cases, such an 

 admission is extremely difficult. As new characters some- 

 times appear by bud-variation, which do not occur in the 

 parent-species or in any allied species, we may reject, at least 

 in these cases, the idea that they are due to reversion. Now 

 it is well worth while to reflect maturely on some striking 

 case of bud-variation, for instance that of the peach. This 

 tree has been cultivated by the million in various parts of the 

 world, has been treated differently, grown on its own roots 

 and grafted on various stocks, planted as a standard, trained 

 against a wall, or under glass; yet each bud of each sub- 

 variety keeps true to its kind. But occasionally, at long 

 intervals of time, a tree in England, or under the widely 

 different climate of Virginia, produces a single bud, and this 

 yields a branch which ever afterwards bears nectarines. 

 Nectarines differ, as every one knows, from peaches in their 

 smoothness, size, and flavour ; and the difference is so great 

 that some botanists have maintained that they are speci- 

 fic-all}- distinct. So permanent are the characters thus 

 suddenly acquired, that a nectarine produced by bud- variation 

 has propagated itself by seed. To guard against the supposi- 

 tion that there is some fundamental distinction between bud 

 and seminal variation, it is well to bear in mind that 

 nectarines have likewise beon produced from the stone of the 

 peach ; and, reversely, peaches from the stone of the nectarine. 

 Kow is it possible to conceive external conditions more 

 closely alike than those to which the buds on the same tree 

 are exposed ? Yet one bud alone, out of the many thousands 

 borne by the same tree, has suddenly, without any apparent 

 cause, produced a nectarine. But the case is even stronger 

 than this, for the same flower -bud has yielded a fruit, one- 



