362 Ever-sporting Varieties 



not apparent as long as each plant produces 

 only one or two, or, at most, a few instances of 

 the same deviation. On the contrary, any ex- 

 isting regularity must betray itself, as soon as 

 a larger number of instances is produced. A 

 rule of periodicity becomes most clearly mani- 

 fest in such cases. 



This rule is shown by no other race in a more 

 undoubted and evident manner than by the 

 ^^ five-leaved " clover. Evidently the several 

 degrees of deviation, going from three to seven 

 leaflets, may be regarded as responses to differ- 

 ent degrees of variation, and their distribution 

 over the stems and branches, or over the whole 

 plant, may be considered as the manifestation of 

 the ever-changing internal tendency to vary. 



Considered from this point of view, my plants 

 always showed a definite periodicity in tliis dis- 

 tribution, which is the same for the whole plant. 

 Each of them, and each of the larger branches, 

 begin with atavistic leaves or with slight devia- 

 tions. These are succeeded by greater devia- 

 tions, but only the strongest axes show as many 

 as seven leaflets on a stalk. This ordinarily 

 does not occur before the height of development 

 is reached, and often only towards its close. 

 Then the deviation diminishes rapidly, return- 

 ing often to atavistic leaves at the summit of the 

 stem or branch. I give the numbers of the 



