EXPLANATORY NOTES, 
As combining delicacy of texture with beauty of form, no 
class of F erns can at all compare with those contained in the two 
genera Hymenophyllum and Tricliomanes. From the wonderful 
transparency of the fronds of many of them, the name of 
“ Filmy Ferns ” lias been given to the tribe. Not a few are so 
extremely tbin that “ Diamond print ” may be easily read through 
their fronds. When laden with moisture, — and especially with 
moisture condensed upon the fronds, by precipitation from the at- 
mosphere, and reflecting a powerful light, no polished emeralds 
can surpass the sparkling brilliancy of the drops which hang at 
the tips of almost every pinnule. Inhabiting shady ravines and 
damp forests chiefly in mountain districts where the air is always 
charged with moisture, these require a degree of humidity in the 
atmosphere much beyond what is needed for other ferns. Not a 
few of the most beautiful enjoy a very cold and damp climate, 
thriving vigorously with a temperature but few degrees above 
the freezing point ; while some ( and probably all the charming 
species of Southern Chili ) bid fair to prove perfectly hardy in our 
climate under the conditions in which our own mountain species, 
H. Wilsoni , thrives. They must not be frozen dry (though some 
of them will bear even this !), but if buried in snow, or frozen 
into a solid mass of ice, will “thaw out” as though they had 
