110 



THE FERN BULLETIN 



Forms similar to those produced by the sensitive 

 fern have been found on its near ally the ostrich fern 

 (0. Struthiopteris or Struthiopteris Germanica) and 

 experiments have shown that they may be produced 

 in the same way. Like the forms of the sensitive fern 

 they have the tips of the pinnae more expanded than 

 the bases, following the well-known rule of develop- 

 ment in the ferns, by which the tips are last to mature. 

 From this it appears that often after the general plan 

 has been decided upon for a particular leaf, there is 

 still time to almost completely change the nature of 

 the tip. 



The production of these obtusilobata forms throws 

 additional light upon that form of the cinnamon fern 

 which has been named frondosa. This, also, is mani- 

 festly formed from a fertile frond and is likely due to 

 some injury to the sterile ones. Unlike the sensitive 

 fern these abnormal fronds cannot usually be produced 

 the same year that the sterile fronds are removed, pos- 

 sibly because the fertile fronds are too far along in 

 development at the time the sterile fronds are pro- 

 duced. It is likely that any effects of cutting off the 

 sterile fronds would not show until the following year 

 and such is the vigor of this species that the removal 

 of two crops of fronds may be necessary to get re- 

 sults. Upon this point information is lacking and 

 carefully conducted experiments by some fern en- 

 thusiast are much to be desired. 



The drawing of Onoclea sensibilis obtusilobata pre- 

 sented is of a specimen from the writer's collection 

 which closely matches the figure given by Eaton in 

 his "Ferns of North America." Eaton gives no figure 

 of the similar form for the ostrich fern though he was 

 familiar with it; in fact while this form is well-known 



