INTRODUCTION. \i 



produced in every garden, and that improvements of 

 the most remarkable kind are yearly occurring in conse- 

 quence. Experiments are, however, it may be supposed, 

 sometimes made without the operator being exactly 

 aware either of the precise nature of the action to which 

 he is trusting for success, or of the limits within which 

 his experiments should be confined. 



Cross fertilisation 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 spontaneous 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. 



When a grain of pollen comes in contact with the 

 stigma, it bursts and discharges its contents among the 

 lax tissue upon which it has fallen. The moving par- 

 ticles descend through the tissue of the style, until one, 

 or sometimes more, of them finds its way, by routes 

 specially destined by nature for this service, into a little 

 opening in the integuments of the ovulum or young 

 seed. Once deposited there, the particle swells, increases 

 gradually in size, separates into radicle and cotyledons, 

 and finally becomes the embryo, that part which is 

 to give birth, when the seed is sown, to a new in- 

 dividual. 



Such being the mode in which the pollen influences 

 the stigma and subsequently the seed, a practical conse- 

 quence of great importance necessarily follows, viz. that 

 in all cases of cross fertilisation the new variety will take 

 chiefly after its polliniferous or male parent ; and that 

 at the same time it will acquire some of the constitu- 



