MAKING NEW KINDS OF PLANTS 



449 



There is a well-known freak or monstrosity occur- 

 ring in many species of plants in which the leaf 

 splits lengthwise more or less completely. This occurs 

 occasionally among the Red Clover 

 plants just described, and gives rise 

 to leaves with higher numbers (four 

 to fourteen) . For example, a five- 

 leaf may, by splitting, become a 

 ten-leaf, such as is shown in Fig. 

 252. Professor de Vries believes 

 that this is to be classed as a mon- m Ten ' leaved Clover ' 

 strosity and is quite different from the four-, five-, 

 six-, and seven-leaves just described, which are due 

 to fluctuating variation and obey mathematical laws. 

 It occurs rarely, appears and disappears suddenly, 

 bears no constant relation to the whole number of 

 leaves, and is to be classed as a sudden variation. 



Occasionally a Clover leaf is met 

 with of the form shown in Fig. 253. 

 It might at first sight be classified 

 as one of the abnormalities just 

 described. When we consider, how- 

 ever, that the arrangement of the 

 leaflet in two rows, one each side 

 of the stalk, is the same as that 

 possessed by the allies of the Clover 

 and the arrangement which the ancestors of Clover 

 itself probably had a long time ago, it seems prob- 



cc 



253, Atavistic Clover 

 leaf. 



