26 Descent 



from other plants, must be carefully excluded. 

 A special lecture will be devoted to this very in- 

 teresting source of impurity and of uncertainty 

 in ordinary cultures. 



Of course, crosses may lie in the proposed 

 line of work, and this is the third point to be 

 alluded to. They must be surrounded with the 

 same careful isolation and protection against 

 bees, as any other fertilizations. And not only 

 the seed-parent, but also the pollen must be 

 kept pure from all possible foreign admixtures. 



A pure and accurately recorded ancestry is 

 thus to be considered as the most important 

 condition of success in experimental plant- 

 breeding. Next to this comes the gathering of 

 the seeds of each individual separately. Fifty 

 or sixty, and often more, bags of seeds are by no 

 means uncommon for a single experiment, and 

 in ordinary years the harvest of my garden is 

 presers^ed in over a thousand separate lots. 



Complying with these conditions, the origin 

 of species may be seen as easily as any other 

 phenomenon. It is only necessary to have a 

 plant in a mutable condition. Not all species 

 are in such a state at present, and therefore I 

 have begun by ascertaining which were stable 

 and which were not. These attempts, of course, 

 had to be made in the experimental garden, and 

 large quantities of seed had to be procured and 



