324 CROSS FERTILIZATION. 



from generation to generation ; but we know that it does 

 take place. Now if the general qualities of a given variety 

 are concentrated in the embryo under any circumstances, it 

 is reasonable to suppose that they will be most especially 

 concentrated in a seed taken from that part of a tree in which 

 its peculiar good qualities reside in the highest degree. For 

 instance, in the fruit of an apple growing upon a north wall 

 there is a smaller formation of sugar than in the same variety 

 growing on a south wall ; and it can be easily understood 

 that the seed of that fruit which is itself least capable of form- 

 ing saccharine secretions, will require from its parent a less 

 power of the same nature than if it had been formed within 

 a fruit in which the saccharine principle was abundant. It 

 should therefore be always an object with a gardener, in se- 

 lecting a variety to become the parent of a new sort, to sti- 

 mulate that variety by every means in his power to produce 

 the largest and the most fully ripened fruit that it is capable 

 of bearing. The importance of doing this is well known in 

 regard to melons and cucumbers, and also in preserving fu- 

 gitive varieties of flowers ; but it is not generally practised 

 in raisins: fruit trees. 



CROSS FERTILIZATION. 



The poiver of procuring intermediate varieties by the inter- 

 mixture of the pollen and stigma of two different parents is, 

 however, that which most deserves consideration. We all 

 know that hybrid plants are constantly produced in every gar- 

 den, and that improvements of the most remarkable kind are 

 yearly occurring in consequence. Experiments are, however, 

 it may be supposed, sometimes made without the operator 

 being exactly aw are either of the precise nature of the ac- 

 tion to which he is trusting for success, or of the limits with- 

 in which his experiments should be confined. 



Cross fertilization is effected, as every one knows, by the 

 action of the pollen of one plant upon the stigma of another. 

 The nature of this action is highly curious. Pollen consists 

 of extremely minute hollow balls or bodies ; their cavity is 

 filled with fluid, in which swim particles of a figure varying 

 from spherical to oblong, and having an apparently sponta- 

 neous motion. The stigma is composed of very lax tissue, 

 the intercellular passages of which have a greater diameter 

 than the moving particles of the pollen. 



