258 THE SENSITIVE AND OSTRICH FERNS. 



in shape, and upon examination prove to be much like 

 the sterile pinnae, except that each edge is tightly rolled 

 over to the midrib, forming two parallel chambers in 

 which the sori are enclosed. Cut across the end, a pinna 

 reminds one of two tiny gun-barrels and the likeness 

 is heightened by the black, powdery spores that sift out. 

 The books are either silent in regard to the indusium, 

 or assert that this species has none, but according to 

 Eaton there is a scale-like indusium at the base of each 

 sorus. This is only to be seen in very young fronds 

 and resembles that of Onoclea. Fronds intermediate be- 

 tween fertile and sterile are occasionally found, and 

 may be produced artificially by cutting off the sterile 

 fronds early in the year. The sterile fronds die in au- 

 tumn but the fertile, like those of the sensitive fern, 

 survive the winter, although to all appearances dead. 

 The spores are not released until spring, when they 

 readily germinate. Since they contain chlorophyll they 

 are not able to retain their vitality for much longer than 

 a year. 



When the ostrich fern gains a foothold in a locality, it 

 spreads rapidly by means of stolons. These are de- 

 veloped from adventitious buds on the rdjfsr6*ck at the 

 bases of the old fronds. Large numbers ^Wlrem remain 

 dormant but a few usually develop into sfflffoer runners 

 that wander a-bout in the earth and finally throw up a 

 new crown of fronds from the tip at some distance from 

 the parent plant. 



The common name is due to an imagined likeness of 

 the fronds to an ostrich feather. It is sometimes known 

 as ostrich-feather fern. In Europe it has been called 

 two-ranked fern because its fertile fronds have two rows 

 of fruiting pinnules. The name of shuttlecock fern is 



