82 



THE FERN BULLETIN 



opposed by several botanists. When I published my 

 little book on the biology of ferns I called attention to 

 this peculiar form and accepted Prof. Underwood's 

 suggestion as the one which is in accordance with what 

 some of us believe to be a law of nature. When this 

 book was reviewed in Nature, this theory was severely 

 criticised and this criticism was the immediate cause of 

 my undertaking the experiments to determine the cause 

 of this abnormal form for I firmly believed that these 

 forms could be readily produced by artificial treatment 

 in the case of this species. I accordingly took my knife, 

 and going to the spot where the ferns grew in great 

 abundance, cut off the leaves (about the 10th of May 

 1894) which were then about one foot high. In the 

 course of another month, the new sterile leaves which 

 had grown up were cut down and again in two weeks 

 so that the third crop of sterile leaves was cut off be- 

 fore there was any sign of the fertile leaves appearing, 

 either in the experimental plot or where the leaves had 

 not been disturbed. The latter part of June and early 

 in July the plants which had been operated on had de- 

 veloped a large number of the abnormal forms of the 

 fruiting leaf while in the adjacent plots, where the 

 leaves had not been disturbed, none of the abnormal 

 forms were present. Twenty-five or thirty of the 

 plants which showed a series of every gradation 

 from perfect fruiting leaves to completely sterile 

 leaves were taken to my laboratory and photo- 

 graphed and all of these were preserved natural size 

 so that any "doubting Thomas" who should come 

 along could see the specimens as convincing argument 

 of the effectiveness of the experiment. In all these 

 gradations the terminal portions of the leaves, pinnae 

 and pinnules, were more expanded than the proximal 



