THE WOOD FERNS. 143 
ing the regular- 
ity of the rows. 
The indusia are 
minutely glandu- 
lar. According 
to some authors 
a third set of 
‘fronds intermedi- 
ate in size be- 
tween fertile and 
sterile and which 
may or may not 
bear sporangia is produced in late summer. This state- 
ment would seem to need confirmation. The fronds 
show their kinship to crzstatum by the fact that the fer- 
tile wither in autumn, while the sterile remain green 
through the winter. 
This species is found from Nova Scotia to Virginia 
and Minnesota and is also reported from Alaska. It is 
most abundant in wet shady places and is especially fond 
of swampy alder thickets. It appears to be fairly com- 
mon, although in comparison with other wood ferns, it 
is rare in collections. 
The Spinulose Shield Fern. 
The spinulose shield fern (A spidzum spinulosum) and its 
varieties are among our commonest species, but their 
abundance in no wise detracts from their beauty. They 
are most plentiful in deep moist woods where they flour- 
ish in the shelter of rocks and large trees or arch along 
the mossy banks of streams. 
The species may be distinguished from its relatives 
and from nearly all our other ferns by its finely divided 
Aspidium Bootti?, Lowest pinna. 
