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fern series this variety first appeared in Louisiana, and takes 

 its name from the town of its origin, "Gretna." 



In using this material in the laboratory, pupils have usually 

 been asked to make diagrammatic outline sketches of the Boston 

 fern type of pinna with one or two of the mutative types, to 

 emphasize the visible differences. In their notes, emphasis was 

 placed on the inherited character of such variations and the fact 

 that this constituted them as mutations. At the same time, by 

 way of comparison, they were usually given the chance to exam- 

 ine some type of spotted bean, such as the "yellow eye," which 

 had a large pigmented area on a white background. These were 

 used to illustrate the "fluctuating" type of variation, as offering 

 differences grading by imperceptible steps into the parent form 

 and not repeated in inheritance, anyone of which might give 

 rise in reproduction to a complete series of color spot gradations. 



That evolution if has taken place, must have occurred by 

 means of inherited variations will be accepted as axiomatic, 

 regardless of whether one believes all variations proceed from the 

 stimulation of hybridization or through spontaneous variation 

 of some unexplained cause. That the student who has examined 

 material of the kinds presented here will thereafter always carry 

 a clearer conception of what is meant by variation, and a better 

 understanding of the relation of this process to evolution seems, 

 to the writer, to be a justifiable conclusion. 

 Brooklyn Botanic Garden 



