Watson.—Sphagna : Habitats , Adaptations , and Associates. 537 
found below 700 feet in this agricultural county. The only places below 700 
feet where Sphagna are found are on the flanks of the hills, a Myrica heath 
near Chard, an Old Red Sandstone area near Bristol, and isolated areas on 
the peat-moor of Central Somerset. The Sphagnum occurring at the lowest 
elevation (50 feet) is S', subnitens (= S. plumidosunb), and this species is also 
present near the summit of Dunkery Beacon, the highest (1,700 feet) hill in 
Somerset. The distribution of the different species growing in the county has 
also been worked out, but the altitudinal range is too limited and human 
interference has been too prominent for any useful result to be attained by 
more detailed and specific mapping of the data available. The map, however, 
clearly shows the preference of Sphagnum for non-calcareous areas. In the 
hilly Mendip region of East Somerset it only grows in a few isolated areas 
where inliers of Old Red Sandstone occur* whilst on the surrounding Carboni¬ 
ferous Limestone it is entirely absent. The central peat-moor (Sedgemoor) 
is chiefly on a substratum of Jurassic calcareous beds with alluvial clays and 
a few recent marine beds, and it is only in the uncultivated areas where the 
calcareous character is neutralized that Sphagnum occurs, and such patches 
are isolated and rare. All the other Sphagnum regions are underlain by 
siliceous and argillaceous rocks, especially those of the Devonian and Old 
Red Sandstone system. The geological distribution of Somerset Sphagneta 
may be summarized as follows: 
Devonian:—The hilly region to the west of the county, including 
Exmoor, the Brendons, and the Quantocks. 
Old Red Sandstone :—Isolated areas on the Mendip hills and a small 
patch west of Bristol. 
Lower and Mid-Lias argillaceous beds:—Small areas on Chard 
Common and on the Blackdown hills. 
Kimeridge and Oxford Clays of the Oolite :—Small and isolated areas 
on the eastern boundary. 
Greensand :—Portions of the Blackdown hills. 
Detailed maps of some uncultivated or semi-cultivated portion of Scot¬ 
land would probably lead to good results as regards the range in altitude of 
the different species, but at present sufficient data for such maps are not 
available, though there is some evidence that species such as S', acutifolium, 
S. fuscum> S. rubellum, S. Lindbergii , S. Girgensohnii, and S. papillosum 
should be considered as plants of elevated moorlands, whilst such species as 
S. fimbriatum and S'. Warnstorfii are normally plants of low elevations. 
In Somerset S. rubellum and S. papillosum occur at an altitude of 320 feet, 
and S. Girgensohnii is found at 600 feet, and similar (and even more striking) 
exceptions are known in other counties. 
Little definite information can be given as to the specific endurance of 
sub-halophytic conditions. None of the Sphagna appears to have any 
tolerance of such habitats; they very rarely occur on sand-dunes, and abhor 
