46 Rhodora [Marca 
it is reported to be "kalkstet" or limited to limestone, and thus 
presumably to circumneutral soils,’ as indicated by o in the last 
column of the table opposite this species. Perhaps different varieties 
are passing as Rhododendron lapponicum, corresponding to the two 
Pyrolas above discussed, and to Andromeda glaucophylla and its 
cireumneutral soil variety iodandra.? 
Loiseleuria (Chamaecistus) procumbens is stated by Schroeter? to 
grow in the Alps on both crystalline rocks and limestone, but to be 
surrounded by autogenous humus, so that the soil acidity may be 
fairly high, even on the latter rock. Arctostaphylos alpina, although 
included by Warming! among acid soil plants, is described by 
Schroeter’ and by Thompson‘ as growing on limestone. It is possible 
that it is surrounded by autogenous humus, and that the reaction 
is acid, or else that another variety is represented. A North American 
red-fruited form growing on limestone is regarded by Fernald as 
a distinct species, Arctostaphylos rubra.” Further study of this group 
appears to be needed. 
Vaccinium caespitosum, though most frequent in acid soil localities, 
is noted by Fernald* to grow in one limestone region, the St. John 
Valley in Maine and New Brunswick. However, in this, as indeed 
in the other cases, it would be better to wait for actual soil tests to 
be made before making deductions as to the soil requirements of 
these plants. Even in species showing apparently well-defined reac- 
tions, it 1s possible that further work may in some cases lead to the 
extension of the ranges of reaction as well as the position of the op- 
timum values. "The writer expects to continue such work and hopes 
that others will take it up also, for the more data there are available 
the more certain will be any conclusions that may be drawn. 
In the Acidity 10 column of Table III, the letter n is placed opposite 
a number of members of the Ericoideae and Vaccinoideae to indicate 
! Fries, T. C. E. Botanische Untersuchungen in Nórdlichsten Schweden. Upsala 
1913, page 230. 
? Fernald, M. L. A calciphile Variety of Andromeda glaucophylla. RHODORA, 
xviii. 100 (1916). 
3 Schroeter, C. Das Pflanzenleben der Alpen. Zurich, 1908, page 135. 
* Warming, E., and Vahl, M. Oececology of Plants (English translation). Oxford, 
1909, pp. 211, 213. 
5 Op. cit. p. 158. 
ë Thompson, Harold S. Alpine plants of Europe. London, 1911, p. 183. 
? Fernald, M. L. The alpine Bearberries and the generic Status of Arctous. Ruo- 
DORA, xvi. 21 (1914). 
3 Ruopora, ix. 163 (1907). 
