149 



This does not establish just what the process of variation is; 

 it merely makes obvious the fact of its occurrence, and it is 

 evident also, that whatever happened must have taken place 

 somewhere along the stolon or reproductive branch from which 

 the different buds arose. Further inquiry and speculation as to 

 the exact nature of variation must wait until some later lessons 

 in which the cell basis of reproduction and heredity, and of pos- 

 sible gene modification can be examined. 



The third figure, showing the representative pinnae of the 

 same leaves shown in figure 2, makes clearer just what types of 

 differences have occurred as a result of the variation process 

 in the Boston fern. When it is realized that these differences 

 parallel to some extent the characteristics which distinguish 

 recognized fern species, added emphasis is given to their possible 

 significance. When, in addition, consideration is given to the 

 extremes of modification developed through secondary and 

 further variation in this same group of ferns, resulting in the 

 scores and scores of well distinguished varieties, a new under- 

 standing should attach both to the meaning of variation as a 

 process and to its underlying significance in any consideration 

 of the whole process of evolution. Space does not permit any 

 other illustration of the wide variety of size and form repre- 

 sented in the whole series of Boston fern mutations which has 

 been presented elsewhere. However, a chart showing the genea- 

 logy of a large number of the named varieties which had been 

 introduced up to about ten years ago is reproduced, taken from 

 another source. As it happens, the wave of interest on the part 

 of florists in introducing new types of these ferns has practi- 

 cally ceased, owing to a variety of factors. 



Besides the varieties which have been introduced commer- 

 cially with names, scores of others have been noted by florists 

 which, while distinctive enough, did not appear to offer com- 

 mercial possibilities and so did not attain to the dignity of 

 being named. Dozens of new forms have appeared in the col- 

 lections at the Brooklyn Botanic Garden during the years of 

 experimental culture, most of which have been described in 

 various reports, although without special names. 



Some reference to the specific varieties illustrated and their 

 most obvious distinguishing characteristics will be appropriate. 

 Four different kinds of variation are represented among these 

 primary-sports of the Boston fern : (1) increase in division, from 



