PRACTICAL INFERENCES. 131 



is proposed to sow. The increased vigour and degree of 

 fertility resulting from this process have been commented 

 on by Darwin. . 



Cross Breeding by means of artificial fertilisation is an 

 operation not so much within the power of an ordinary 

 agriculturist, owing to the delicacy of manipulation and 

 length of time required to ensure results worth having. 

 Such experiments would be better accomplished in the 

 laboratory or experimental garden of the professed physio- 

 logist. The experiments carried out by Andrew Knight, 

 Maund, and Sheriff in the case of wheat and oats are, 

 however, encouraging. When undertaken for practical 

 purposes, it is specially desirable that mere hap-hazard 

 crosses should not be encouraged, much less made purposely, 

 but that a definite object should be pursued in a definite 

 manner. The experimenter should set himself to work to 

 endeavour to produce an earlier, a hardier, a more prolific 

 variety, as the case may be, selecting for his purpose such 

 varieties to breed from as he has ascertained by experience 

 to be of such a nature as likely to yield promising results. 

 It is not possible to give detailed instructions here as to the 

 way in which cross-breeding may be carried out; it is 

 difficult with cereals, less so with leguminous plants, easiest 

 with the cabbage tribe. Indeed, as growers know to their 

 cost, it is difficult to keep the races or strains of the 

 cabbage-tribe pure and uncontaminated, owing to the facility 

 with which the flowers are fertilised by insects which bring 

 the pollen from the flower of some other variety. Too high 

 breeding, however, often entails a delicacy of constitution 

 or a defective productiveness which may be overcome by a 

 fresh cross with a stronger strain. 



K 2 



