362 Ever-sporting Varieties 



not apparent as long as each plant produces 

 only one or two, or, at most, 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 the '' five- 

 leaved ' ' clover. Evidently the several degrees 

 of deviation, going from three to seven leaflets, 

 may be regarded as responses to different de- 

 grees 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 this dis- 

 tribution, which is the same for the whole plant. 

 They all begin with atavistic leaves or with 

 slight deviations. They are succeeded by 

 greater deviations, 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 rapid- 

 ly, returning often to atavistic leaves at the 

 summit of the stem or branch. I give the num- 

 bers of the leaves of a branch, in their order 



