Observations upon some Noteworthy Leaf Variations. 299 



which is certain to reward the diligent and competent student 

 with evidence of the highest value ; and it is probably safe to 

 assert that the palseobotanist of the future will devote his at- 

 tention more exclusively to the latter source of evidence, 

 utilizing the former only so far as it may prove serviceable for 

 purposes of confirmation. 



My attention has been directed recently, to another ex- 

 ample of leaf variation which not only serves to emphasize the 

 conclusions already reached in several important respects, but 

 it is remarkable and of more than usual scientific interest be- 

 cause it affords direct and positive proof as to the nature of 

 certain structural alterations and the conditions under which 

 they arise ; while it also exhibits a completion of such changes 

 within so short a period as to make the entire history one of 

 easy record. 



About five years ago a somewhat remarkable sport was 

 developed in the conservatories of the F. R. Pierson Com- 

 pany, at Tarrytown-on-Hudson, from the well known, so-called 

 Boston fern, Nephrolepis exaltata. This sport showed such 

 unusual characteristics and gave promise of such possibilities, 

 that careful cultivation followed with the production of what is 

 now known as Pierson's fern. In 1902 this plant was ex- 

 hibited at the March show of the Massachusetts Horticultural 

 Society, and received an award of the Gold Medal as being 

 " by far the most important and remarkable plant that has 

 been shown before this Society for many years." ' This ver- 

 dict is fully sustained by the plant, which possesses a decora- 

 tive effect of the highest value ; but as we are now concerned 

 with its scientific aspects, such considerations must be left to 

 the horticulturist. 



From information kindly supplied by the F. R. Pierson 

 Company, it seems that this plant developed abruptly among 

 a large number of plants of Nephrolepis exaltata which were 

 being grown for commercial purposes. It did not result from 

 unusual conditions of nourishment and care immediately suc- 

 ceeding a period of arrested development, nor was it the pro- 

 duct of any other unusual conditions of environment. It 



1. Trans. Mass. Hort. Soc, 1902, Part II, 145, 160. 



