FLOWERS OF THE HEATHS AND MOORS 1 



The plants which are found on heaths and moors are those that 

 require humus in a sour (or acid) and free state. The soil is barren 

 and not rich in nitrogen that can be readily assimilated, and conse- 

 quently unsuited for cultivation. The soil is not rich in lime, and in 

 this respect differs from some marshes, but is similar to that of bogs, 

 which indeed are usually interspersed amongst heaths and moors. But 

 there are in some cases upland marshes which are comparatively rich in 

 lime and peat. The soil of a bog or fen on deep peat, however, is 

 acid, not alkaline in reaction. 



The raw humus covers a sterile subsoil of diverse character. Of 

 ericetal species there are about 80, of which we describe 29 here. 

 More than all other plants, even on wet soils, heath plants are xero- 

 philous, and we see in them adaptations to physiologically dry con- 

 ditions. Heaths are exposed to the wind like halophytic vegetation, 

 and few trees grow on such tracts, except in the low moors. Many 

 marsh plants grow there also. The adaptations to xerophytic conditions 

 include a felt of hairs on the under surface of the leaf, as in the 

 Creeping Willow, and this serves the purpose of keeping open the 

 pores or stomata on the leaves, and at the same time depresses trans- 

 piration. Papillae surround or project over the pores for the same 

 reason in sedges. A coating of wax covers the leaf in the Rosemary 

 and Cranberry (see last section). Many stems and leaves are excep- 

 tionally thick, and the above are also sclerophyllous. Filiform or 

 threadlike leaves are developed. Heaths, Ling, and Cotton Grasses 

 are comparatively all but leafless. Some leaves present their edges to 

 the light, as in Iris and Asphodel. 



The adaptation to dry conditions is connected with the soil char- 

 acters. The soil is physiologically dry. There are, however, some 

 genera which include marsh or bog species, and others that require a 



1 Cf. Section X, where moors are dealt with in some detail in discussing bogs and marshes also. It 

 is the wetter types of moors that are specially referred to there. 



VOL. V. C5 67 



