POLYSTICHUM. 157 



what crescent-shaped, for they have, as is universal in the 

 British forms at least of this genus, the upper base extended 

 into a small auricle, or enlarged lobe, and the lower base as 

 it were abscised ; while the apex is tapered off to an acute 

 point, and the margin is serrated, with spiny teeth. 



The veins are alternately branched, and do not join 

 together or anastomose, but extend free to the margin ; and 

 the fructification, which is generally abundant, and often 

 crowded, is ranged in a line on each side the midrib of the 

 pinnules, and also on the larger pinnules on each side the 

 midvein of the basal lobes or auricles. The indusium is 

 circular, and attached by a little depression or stalk in its 

 centre. 



A variety called lobatum, and considered a distinct species 

 by some botanists, differs chiefly in the narrow outline of 

 the frond, the pinnules of which are much more decidedly 

 decurrent ; indeed, every possible variation in the consolida- 

 tion of the pinnules is to be met with, between the ordinary 

 bipinnate form of PolysticJium aculeatwm, and a simply 

 pinnate form of the species, which, from its resemblance to 

 P. Lonckitis, has been called lonchitidioides. This latter 

 form, however, owing its origin to the peculiar circumstances 

 of growth only, cannot properly be recognized as a variety, 



