LECTURE XIX 



EXPERIMENTAL PEDIGREE- CULTURES 



The observation of the production of mutants 

 in the field at Hilversum, and the subsequent 

 cultivation of the new types in the garden at 

 Amsterdam, gives ample proof of the mutability 

 of plants. Furthermore it furnishes an analogy 

 with the hypothetical origin of the swarm of 

 species of Drab a and Viola. Last but not least 

 important it affords material for a complete 

 systematic and morphologic study of the new- 

 ly arisen group of forms. 



The physiological laws, however, which gov- 

 ern this process are only very imperfectly re- 

 vealed by such a study. The instances are too 

 few. Moreover the seeds from which the mu- 

 tants spring, escape observation. It is simply 

 impossible to tell from which individual plants 

 they have been derived. The laevifolia and the 

 brevistylis have been found almost every year, 

 the first always recurring on the same spot, the 

 second on various parts of the original field. It 

 is therefore allowable to assume a common 



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