Sphagna, their Habitats, Adaptations, and Associates. 1 
BY 
W. WATSON, D* Sc* 
With five Figures in the Text. 
INTRODUCTION. 
T HE familiar names of bog-moss, turf-moss, and peat-moss indicate the 
general habitats of the different species of Sphagnum , since they are 
all found in places where peat is present, and in most cases where the ground 
is wet and has that yielding character which is associated with the word 
boggy. The degree of bogginess varies greatly; in some cases the 
Sphagnum layer conceals a treacherous depth, in others a firm substratum 
is quickly reached. In exceptional cases peat is absent or almost so, but if 
not present in the particular spot where the Sphagnum actually grows can 
be found in the near vicinity. Sphagnum inundatum , S’. subnitens , S'. re¬ 
cur v um, and other species are sometimes found on the sides of furrows cut 
by streamlets, or in other spots where the immediate presence of peat is not 
apparent, but usually little search is necessary to establish the presence of 
peat in the neighbourhood. One of the most striking cases of this kind 
noticed by the author occurs by the side of a sloping hard-metalled road on 
the Blackdown Hills in Somersetshire. S'. pulchrwn is present in fail- 
quantity and seems to obtain its supply of water from the inconstant 
drainage after rain ; the district, however, is turfy and further search reveals 
the presence of patches of 5 . recurvum which are constantly moist and have 
a somewhat peaty substratum. Sphagna sometimes occur on moist rock- 
ledges which have little or no peaty covering. This very rarely happens in 
lowland or even in upland districts, but is not uncommon on sheltered 
alpine or subalpine ledges, where the moisture from the clouds forms no 
inconsiderable part of the water-supply. As concrete instances of this 
habitat noticed by the author the following may be given: A. acutifolium 
on moist rock-ledges, altitude 3,500 feet, Ben Doran, Argyllshire ; S', mollus- 
cum , with a similar habitat on the same mountain, but at a lower elevation 
(2,500 feet) and in company with Scapania ornithopodioides. 
When the water is squeezed out of these tufts of Sphagnum it is found 
to be more or less acid ; the peat derived from its decay seems to retain this 
1 This paper forms part of a thesis for the degree of Doctor of Science, London. 
[Annals of Botany, Vol. XXXII. No. CXXVIII. October, 1918.] 
