SENSITIVE FERN 



Onoclea sensihilis L. 

 T3ATriER coarse, largfe ferns -witli anastomosing veins, 

 •'-^ sterile and fertile fronds, very unlike. Sterile leaves, 

 broadly triangular, divided into several long narro-w divisions 

 which form distinct pinnae in tke last pair, contracted at tKe 

 base; upper divisions connected by a wing, finally confluent 

 at the apex; margins of tlie upper divisions entire or wavy, 

 the lower becoming more deeply scalloped. Stems of sterile 

 leaves very long, yellow, arising singly and all summer from 

 a slender sKalloAv creeping rootstock whicK is mucK branched; 

 the entire leaf from a few inches to t-wo feet or more m 

 length. Fertile leaves shorter and erect, produced in groups 

 in enrly summer, persistent through winter; the blades twice 

 compound, the pinnules contracted and rolling up to form 

 dark green berry-like structures which turn dark brown, 

 opening the follo\ving spring to discbarge the spores. Sori 

 rounded; mdusia very delicate, hood-like, early withering. 

 Forms intermediate betAveen fertile and sterile leaves occa- 

 sionally round. 



1 his common fern, one of the tw^o species of Onoclea in 

 the Dells, grows in low, moist open ground, often forming a 

 border or mass along the streams. The common name seems 

 inappropriate; but the sterile leaves wither quickly when 

 picked, and are sensitive to early frosts. 



