THE WOOD FERNS. 



foliage. The blade is nearly three 

 times pinnate, the ultimate pin- 

 nules being small, oblong, blunt 

 at the ends and spinulose 

 toothed. The cutting, however, 

 varies greatly. The secondary 

 divisions are not always com- 

 pletely pinnate but they are al- 

 ways so near it as to give a very 

 delicate, lace-like effect to the 

 frond. The pinnules on the in- 

 ferior side of the pinnae are fre- 

 quently elongated especially in 

 the lowest pair, a characteristic very com- 

 mon in this family. The sori are borne 

 on the backs of ordinary fronds in what 

 approximates a double row on each of 

 the secondary divisions, a sorus being 

 located at the base of each pinnule. It 

 not infrequently happens, however, that 

 the pinnules themselves bear one or more 

 sori which breaks up the regularity of 

 the rows and makes the arrangement of 

 the fruit dots less definite than it is in 

 other species. The indusium is kidney- 

 shaped and smooth. The sporangia early 

 turn to a shining black and do not be- 

 come brown until late in the season. 

 The fronds are produced from a short 

 stout rootstock and all appear in early 

 spring. 



The two varieties of this species are so much like it in 

 appearance that good students cannot always agree as to 



SPINULOSE 

 SHIELD FERN. 



Asfidiunt spinulosum 

 intermedium. 



