HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 177 
It is typically developed on relatively poor sandy and gravelly soils, 
whose climate is wetter than that which gives rise to steppe, the 
climate of which is too dry for tree growth. Heath may exist side by 
side with woods and may represent a degeneration of woodland. 
Heath occurs in Europe in regions with an annual rainfall between 
25 and 40 inches (60 to 100 cm.), but the Cornish heath and those of 
the eastern Highlands of Scotland often receive a rainfall of between 
40 and 60 inches (100 to 150 cm.) in the year. The Scottish heaths 
develop a deeper layer of relatively pure acid humus, up to 8 or 12 
inches (20 to 30 cm.), according to Hardy. The East Anglian heaths 
have a rainfall of 25 inches, or less, and a minimum of dry peat forma- 
tion, while the heaths of the southeastern counties have a layer of dry 
peat seldom more than a fraction of an inch in thickness passing down 
into sand darkened by humus. The surface layer of dry peat is 
formed by lichens and mosses, which are pioneers on denuded soils. 
Drude in his comparison of the flora of Great Britain with that 
of Central Europe® believes that the lowland heaths, the “heath asso- 
ciation”’ or “Callunetum arenosum”’ of Tansley, for the most part 
correspond with those of northwestern Germany in the region of the 
Weser and the Ems, and on the English heaths one would often feel 
oneself transported to Germany, if it were not for the sudden oc- 
currence of Erica cinerea between Erica tetralix and Calluna vulgaris, 
or of Ulex minor, or Ulex gallit with masses of Schoenus nigricans, 
Myrica gale, Narthecitum and Hypericum elodes, which indicate the 
west European conditions. 
If there is a physiognomic similarity in the heathland of England 
and northwest Europe, then we must determine the essential character 
of the heath vegetation and the kinds of soils on which it is found, for 
by extension we can apply these characters as a test of heathland in 
other parts of the world. 
Although the soils of the North German plain are the same in the 
east as in the west, according to the researches of Graebner and others, 
yet the vegetation of the two areas is quite distinct. In the west, in 
Hanover, Oldenburg and Schleswig-Holstein, are great stretches of 
heathland, whilst in the east these are entirely absent and are replaced 
by thin pine woods (pine-heath = Kiefern-heide) and a steppe-like 
flora. This difference is due in part to the different climate, for the 
main heathland is west of the Elbe, where the rainfall rarely falls 
below 24 to 28 inches per annum, whereas in the east the rainfall often 
does not exceed 20 inches per annum. In other words, heathland is 
developed with an oceanic climate, while pine-heath is found where 
the climate is continental. The seasonal changes of temperature of 
3 The International Phytogeographic Excursion in the British Isles (1911), p. 93. 
