320 Plant Life and Evolution 



His book, " Die Mutationstheorie," published in 

 1901, attracted at once much attention, and was a 

 great stimulus to the further study of variation in 

 both plants and animals. The basis of this theory 

 is that new species arise, not by the accumulation of 

 slight or fluctuating variations, but by discontinuous 

 variations or sudden leaps, which are immediately 

 of specific value. 



Discontinuous Variations : Sports. Reference 

 has already been made to these discontinuous varia- 

 tions, or sports, of which many have been recorded, 

 especially in cultivated plants. A list of the most 

 important of these has recently been given by Lotsy 

 in his work, " Vorlesungen iiber Descendenz- 

 theorien," 1906. The first of these recorded muta- 

 tions dates back to 1590, when there appeared in 

 the garden of the Apothecary Sprenger, in Heidel- 

 berg, a well-marked variety of Chelidoninm majus, 

 which proved to be constant and reproduced itself 

 perfectly from seed, thus behaving like the " mu- 

 tants " of De Vries. A very widely cultivated plant 

 which is supposed to be a mutant, is the well-known 

 Lombardy poplar, which has been propagated in a 

 purely non-sexual way for a very long time. It is 

 supposed to be a sport from the European Populus 

 nigra. All of the individuals that are known are 

 staminate, and consequently cannot propagate from 

 seed. The purple-leaved, and cut-leaved, varieties 

 of many trees and shrubs, are probably examples of 

 such sports, and many at least have been found to 



