VARIATION. 53 



ance, with the tips of the leaves hanging down limply, and the 

 tips of the branches hanging down, we would pass it, thinking 

 that some accident had befallen it. But if in such a field of 

 clones we notice a plant in this condition, we see that all ten of 

 the same number have this peculiar appearance. We see a 

 plant whose main stalk stands out of the vertical. We might 

 easily think that a mole had passed underneath the plant, if we 

 did not see all ten plants of the number stand askew in the 

 same way. The ten plants of a clone are either all free from 

 fasciations, or they all tend to be fasciated in the same degree. 

 The degree of development of the main stalk, the moment of 

 shooting from the rozette, is always the same for the members 

 of one clone. Some clones will remain rozettes all summer, 

 other will start sending up a stalk very late, in short, all stages 

 of development are present in the field, always with this res- 

 triction, that the individuals of one number are alike. There is 

 so much diversity between clones, that it is always possible to 

 see where one clone ends and the other begins, by observing 

 the general habitus, which is made up of small, inobtrusive 

 diffeences in colour, in branching,in shape. This variation in 

 the field is what goes under the name of individual variation, 

 fluctuating variation. And here we must once more emphasize, 

 that such individual variations are more commonly caused by 

 differences in the genotype than by differences in the circum- 

 stances under which the individuals grow up. 



After one has observed the nature of the variability within 

 clones, and of variabil ty in mixtures, as due to differences in 

 genotype, one begins to be able to distinguish between them. 

 In other words, one develops this "wonderful intuition of the 

 plant breeder" of which the journalists talk so much. It is in- 

 deed very important for anyone who intends to produce new 

 plants to develop this faculty of distinguishing at a mere in- 

 spection between fluctuating variability caused by genotypic 

 diversity and that caused by the environment. And the only 

 way to develop this faculty is by observing very many pure 

 clones. In plant-breeding it is very important to distinguish be- 



