II 49 
Sort ReEacTIONS OF CERTAIN FERNS 
where lime becomes more or less leached from its soils. 
These ferns are both classed as calcareous soil species, 
the latter the more tolerant of acidity. 
Woodsia Ilvensis has been recorded most frequently on 
noncaleareous rocks, comprising sandstone, shale, schist 
and trap, and not a single mention of its occurrence on 
limestone could be found in the literature. One colony 
of it was observed at the extreme top of the Will- 
oughby cliffs, so exposed as to be subjected to thorough 
leaching by the rain, and tests of the soil showed it to be 
somewhat acid, in spite of the calcareous nature of the 
adjacent gneiss rocks. In numerous occurrences of the 
same species in Pennsylvania, as well as one in West 
Virginia, the rocks are sandstone and shale, and the re- 
actions are dominantly subacid. Although not found 
in the most acid soils, this species seems most correctly 
classified as an acid soil plant fairly tolerant of lime. 
The more abundant and widespread Woodsia obtusa 
grows on all sorts of rocks, but is best developed on lime- 
stone. When growing on schist and similar rocks its 
soil reactions have been found to be often subacid, so it 
is classed as a calcareous soil species rather tolerant of 
acidity. 
Fiha (Cystopteris) bulbifera grows, throughout the re- 
gion covered, mostly in talus at the bases of cliffs of 
limestone as well as of various other rocks. Its soils 
are likely to contain considerable leafmold, and to be 
circumneutral in reaction, subacid reactions having been 
but rarely observed. It is evidently to be classed as a 
calcareous soil species, somewhat tolerant of acidity. 
The even more abundant Filix (Cystopteris) fragilis 
grows on ledges of sandstone, schist and shale, as well 
as of limestone rocks, and also in talus and in woods en- 
tirely apart from any rocks. Tests of its soils have 
given about the same results as with the preceding spe- 
cies, but as would be expected from its growth on the 
