18 AMERICAN FERN JOURNAL 
species is recorded, and, as about three tests have cus- 
tomarily been made at each locality, the number of local- 
ities represented is approximately 14 of the number of 
tests. Tests made on soil adhering to the roots of her- 
barium specimens, which seemed desirable in a few in- 
stances to: supplement field data, are distinguished by 
parentheses. 
The terms used for the soil reactions are those re- 
cently proposed;? the numbers are “‘specific acidities’’ 
and “specific alkalinities,’’ and represent the amounts of 
acid or of alkaline constituents (ions) present, with re- 
ference to pure water as a unit. Thus the number 300 
on the acid side means that the corresponding soil con- 
tains that many times as much acid as water contains, 
and so on. All reactions of soils in which the various 
species have been observed to grow are marked with a 
letter x, in lower case for rarely observed values, capitals 
for frequently observed ones, and bold face letters for 
what may be termed optimum values, that is those 
shown by the most luxuriant and flourishing plants. 
The majority of the species tabulated clearly favor 
reactions lying toward one side of the table or the other, 
and it is convenient to have some way of classifying 
them on this basis. Those the dominant reactions of 
which lie toward the left hand side may be termed “acid 
soil plants.”” It should be noted that the degree of acid- 
ity represented by habitats supporting these ferns is for 
the most part less than that of the sphagnum bogs and 
sandy barrens where so-called ‘‘oxylophytes”’ grow, 80 
the latter term is not desirable for application here. 
It is also noteworthy that the acid soil species are 
dominantly southern in distribution. This class is des- 
ignated by an A, for acid, in the last column of the 
table. 
‘Journ. Wash. Acad. Sci. 9, 305-309, 1919. 
