Mutations 75 



character; Icevifolia is characterized by the loss of the 

 crinkling of the leaves ; brevistylis, by the partial loss of 

 the pistil ; and nanella, by the loss of stature. 



5. The new species are produced in a large number of 

 individuals. 



It will be remembered that there were produced a 

 large number of similar mutants in the same year, and 

 also that the same mutations were produced in successive 

 generations. 



There is obviously some cause for the production of 

 these mutations. Whatever the exciting cause may be, 

 the different mutants are not affected in the same way. 

 Oblonga, nanella, and lata are frequently produced, while 

 gigas, rubrinervis, and scintillans are more rare. It has 

 been found through later studies by Gates, Davis, Shull, 

 and others that some of the types formerly thought by 

 de Vries and others to be mutations are hybrids. 



It was found also that when the mutants were crossed 

 together, types were found in the progeny which were 

 the same as produced by (E. Lamarkiana itself. For 

 example, (E. rubrinervis was observed by de Vries 

 to arise in the hybrid progeny of (E. lata x nanella; 

 (E. lata x brevistylis; (E. nanella X brevistylis; and (E. 

 scintillans x nanella. 



In nature, repeated mutations are probably of far more 

 importance than isolated ones. The competition of 

 plants is so great that the chances of the survival of one 

 divergent individual are much less than as if these mutants 

 were repeatedly produced in considerable quantity. 



6. Mutability is distinct from fluctuating variability. 

 The foregoing evidence points to the fact that new 



