90 ASPIDIUM 



MARSH FERN: Aspidium Thelypteris. 



(Nephrodium; Dryopteris.) 



Fronds lance-shaped in outline, slightly nar- 

 rowed at the base, pinnate; pinnae set at right 

 angles to the rachis, rather narrow, cut nearly to 

 the midrib into short, blunt lobes; first fronds al- 

 ways sterile, the fertile fronds not appearing until 

 midsummer. The pinnules of the fertile fronds 

 appear to be narrower and more pointed than those 

 of the sterile ones, owing to their reflexed margins, 

 which nearly cover the fruit dots; stipes long, 

 sometimes twice as long as the blades; veins fork- 

 ing. 



Fruit dots small, borne in two rows on each pin- 

 nule; indusium minute, soon withering, the spo- 

 rangia spreading out and nearly covering the under 

 surface of the pinnule. 



Common in marshes, widely distributed. 



