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POPULAR SCIENCE MONTHLY 





Y 



Sample Leaves op Common Garden Dahlia (Dahlia variabilis), Showing Ordinary 

 Variation within a Species when under Cultivation. 



The process of formation of new types may be grouped under four 

 heads: selection, crossing, hybridization and mutation (or saltation). 

 The process of artificial selection is used in all cases, those varying 

 strains likely to prove useful being preserved, the others destroyed. 

 The word ' crossing ' may be advantageously used for the mingling of 

 strains within a species, and ' hybridization ' for the breeding together 

 of members of different species. The name ' mutation ' (or preferably 

 ' saltation ') is applied to sudden changes of characters for which no 

 immediate cause is apparent. 



