ONOCLEA SENSIBILIS, FORMA OBTUSILOBATA 7 
fronds by mowing or otherwise. In 1894, Prof. G. F. 
Atkinson, testing Underwood’s theory, succeeding in 
producing them artifically by repeated cutting of the 
sterile fronds on certain plants. He concluded that 
Underwood was correct and that the variation was 
caused by semi-starvation, due to injury, which, so to 
say, compelled the plant to use its fertile fronds for 
leaf-functions as well as spore-bearing.’ In 1881,3 
however, and again in 1898, in a paper read at the 
Boston meeting of the Fern Society, Mr. Davenport 
presented a considerable mass of evidence to show, on 
the one hand, that though experiments like Prof. Atkin- 
son’s might result in obtusilobata forms, they failed to 
do so more often than not; and, on the other, that 
plants growing under entirely normal conditions and 
with their full supply of sterile fronds frequently pro- 
duced such forms and that the same plant, under 
apparently unchanged conditions, might have them 
one year and not the next. He argued that, though 
injury might produce them, it did so by stimulating 
a latent tendency which already existed in the plant 
and which might equally be developed by other, less 
obvious stimuli; and suggested that the tendency in 
question might be one toward evolutionary reversion 
to an earlier, non-dimorphic form. Evidence in support 
of his conclusion has been brought forward by Mrs. 
E. G. Britton, Rev. J. A. Bates (at the Boston meeting), 
Mrs. A. E. Scoullar,* W. A. Poyser® and now by Mr. 
Ridlon; and though some have tried, no one seems 
to have repeated Prof. Atkinson’s experiment success- 
fully. 
1 Bull. Soha! Bot. Club 8: 101. 
5 Fern Bull. 17: 76. 1909. 
