THE MARSH FERN TRIBE. 127 
means a little shield, in allusion to the shape of the in- 
dusium. Many of the common names given to members 
of the genus are also derived fromthis shape. Dryopteris, 
sometimes used instead of Aspidzui, is also from the 
Greek and literally means oak-fern. There are upwards 
of one hundred and fifty species distributed throughout 
the world. It is probable that the generic name 
Nephrodium will ultimately be used for these species in 
America. It is the name commonly used abroad. 
