Chap. XXII. CAUSES OF VARIABILITY. 247 



that the one can be readily grafted and succeeds admirably on 

 the other, the fact of variability being thus caused is not sur- 

 prising ; as we are here enabled to see the cause, namely, the 

 very different nature of the stock and graft. Several North 

 American varieties of the plum and peach are well known to 

 reproduce themselves truly by seed ; but Downing asserts, 15 

 " that when a graft is taken from one of these trees and 

 " placed upon another stock, this grafted tree is found to lose 

 " its singular property of producing the same variety by 

 '■ seed, and becomes like all other worked trees ;" — that is, its 

 seedlings become highly variable. Another case is worth 

 giving : the Lalande variety of the walnut-tree leafs between 

 April 20th and May 15th, and its seedlings invariably 

 inherit the same habit ; whilst several other varieties of 

 the walnut leaf in June. Now, if seedlings are raised from 

 the May-leafing Lalande variety, grafted on another May- 

 leafing variety, though both stock and graft have the same 

 early habit of leafing, yet the seedlings leaf at various times, 

 even as late as the 5th of June. 16 Such facts as these are 

 well fitted to show on what obscure and slight causes vari- 

 ability depends. 



'8' 



I may here just allude to the appearance of new and valuable 

 varieties of fruit-trees and of wheat in woods and waste places, 

 which at first sight seems a most anomalous circumstance. In 

 France a considerable number of the best pears have been discovered 

 in woods ; and this has occurred so frequently, that Piteau asserts 

 that " improved varieties of our cultivated fruits rarely originate 

 with nurserymen. 17 In England, on the other hand, no instance of 

 a good pear having been found wild has been recorded ; and Mr. 

 Eivers informs me that he knows of only one instance with apples, 

 namely, the Bess Poole, which was discovered in a wood in Notting- 

 hamshire. This difference between the two countries may be in part 

 accounted for by the more favourable climate of France, but chiefly 



15 ' The Fruits of America,' 1845, Poiteau's remark is quoted in ' Gar- 

 p. 5. dener's Mag.,' vol. iv.. 1828, p. 385. 



16 M. Cardan, in 'Comptes Ren- See ' Gard. Chronicle,' 1862, p. 335, 

 dus,' Dec. 1848, quoted in 'Gard. for another case of a new variety of 

 Chronicle,' 1849, p. 101. the pear found in a hedge in France. 



17 M. Alexis Jordan mentions four Also for another case, see Loudon's 

 excellent pears found in woods in ' Encyclop. of Gardening.' p. 901. 

 France, and alludes to others (' Mem. Mr. Rivers has given me similar 

 Acad, de Lyon,' torn ii. 1852, p. 159). information. 



