50 2 AMERICAN FERN JOURNAL 
rock types first mentioned, it is still more acid-tolerant. 
It avoids, however, mediacid soils. 
Although there has been no opportunity to study 
Dryopteris (Aspidium) fragrans in the field, its relation- 
ships seemed of sufficient interest to make tests on her- 
barium specimens worth while. It has been recorded 
as growing on presumably noncaleareous slate or schist 
in several northern regions; but as appearing most com- 
monly in localities where limestone rocks are dominant, 
although in exposed situations, where the lime might be 
leached out by the rain. The National Herbarium 
contains specimens with soil adherent to the roots from 
the cliffs of schist rocks at Smuggler’s notch, and those 
of limestone conglomerate near Bic, Quebec. As an- 
ticipated, the soil reactions in both of these cases proved 
to be distinctly acid. The acidity is not, however, 
great enough to throw doubt on the correctness of its 
usual classification as a calcareous soil plant, if it is 
regarded, like several others belonging in this class, as 
rather tolerant of acidity. 
Sor Reaction anp PLant RELATIONSHIP 
Close relationship between plants, whether they be 
classed as separate genera, species, or varieties, implies 
derivation either from the same ancestor or from one 
another, by some process of natural selection, mutation, 
or hybridization. Studies of soil reaction, such as are 
described in the present paper, are of course not capable 
of deciding what source or what process were concerned 
in any given case; but when, as in certain of those above 
described, two related plants show a marked difference 
in soil preference or in tolerance to acid or to calcium, it 
is perhaps safe to infer that neither represents a pss: 
day mutant or hybrid of the other. 
In the case of the genus Cheilanthes the data are inade- 
quate for discussion. Of the Pellaeas, however, one, P- 
