Observations upon some Noteworthy Leaf Variations. 303 



except for variations of degree, the same differences exist be- 

 tween members of an individual, as between different indivi- 

 duals, and we may correctly assume that spores which are pro- 

 duced only on unmodified fronds will be incapable of repro- 

 ducing the characteristics of the modified frond. This is borne 

 out by the observed fact that propagation depends entirely upon 

 runners which are developed very freely, and through which 

 the plant multiplies with great readiness. I find, however, that 

 the above statement requires some modification, since it is not 

 true in the strict sense. 



An examination of a plant which was selected at random, 

 shows that while fruit is produced on the unmodified fronds in 

 the usual way, this capacity also extends to transitional forms 

 where the tendency to modification is as yet but feebly ex- 

 pressed. But more than this, I have found that completely 

 modified fronds also bear fruit. The specimens under observ- 

 ation are too immature to determine what perfection such 

 fruit might attain in all cases, but that which is produced at 

 the base of the pinnae is spore bearing, and from this the in- 

 ference might be justified, that even the pinnules are produc- 

 tive of spores. We are therefore compelled to recognize the 

 fact that while the modification of the frond is attended by 

 sterilization, this is not complete, and it is probably of the 

 nature of a temporary loss of functional power which may be 

 restored as the variety becomes more firmly established. For- 

 tunately we are able to avail ourselves of information which 

 has an important bearing upon the correct solution of this 

 question. A similar variety of the Boston fern has recently 

 been produced by Mr. L. H. Foster whose name it bears. 

 This fern, however, is characterized by the fact that the modi- 

 fied fronds do bear spores, though the plant does not exhibit 

 that luxuriance of growth which is so marked a feature in 

 Pierson's fern. 



It is quite clear that transformations of the nature repre- 

 sented by Nephrolepis must have the same bearing upon 

 palaeontological evidence as in the previous cases ; but this 

 plant is of scientific interest in another and far more impor- 

 tant sense, and we are led to ask, what significance have 

 these facts from the standpoint of evolution ? 



