334 MESOPHYTES SECT, xvi 



the former is a shade-enduring tree whose foliage shoots out earlier in 

 spring than that of the oak. Only in humid places for instance, on the 

 low-lying clay soil of Laaland and on the more sterile soil of western 

 Jutland can the oak successfully compete with the beech. 



The high-forest is of very mixed nature, because the demands for light 

 made by the oak are moderate. In German and Austrian oak-forests, 

 Tilia, Acer, Populus tremula, Ulmus, Fraxinus, and Carpinus are inter- 

 spersed ; in France, Fagus and Castanea are often subordinate members 

 of oak-forest. 



In opposition to beech, the oak has beneath it an abundant underwood, 

 which is often formed by a dense bushy growth of Corylus, Crataegus, Acer 

 campestre, Prunus spinosa, Carpinus, Rhamnus Frangula, Euonymus 

 europaea, Salix, Viburnum Opulus, Rubus Idaeus, Lonicera Xylosteum, 

 and others ; of these shrubs the particular species present vary with the 

 nature of the habitat. In certain cases, Juniperus, Pteris, and even 

 Calluna, may occur, especially in oak-forest on poor sandy soil. In 

 Austrian oak-forest there also occur Viburnum Lantana, Ligustrum 

 vulgare, Staphylea pinnata, Daphne Mezereum, and others. 



The soil of oak-forest may be a good, black or greyish-brown, friable, 

 mild humus, inhabited by earthworms. Beneath and between the shrubs 

 forming the bushy underwood flourish numbers of grasses and herbs, 

 which, however, do not produce a continuous carpet of vegetation. 

 Among them are species of Anemone and Viola, Vicia Cracca, Lathyrus 

 macrorrhizus, Hypericum perforatum, H. quadrangulum, Potentilla 

 sylvestris, Campanula rotundifolia, and Achillea Millefolium. In addition, 

 Pteris aquilina plays a prominent part. The majority of plants on the 

 ground of the forest blossom in spring. The soil may also partake of the 

 nature of sour humus ; but the sour humus of oak-forest is very different 

 from that of beech-forest. 1 Now and again oak-forest grows on marshy, 

 badly ventilated soil, or upon fine-grained, dense, sandy soil, or in the 

 flood-zone bounding rivers in sheltered spots. 



Birch-forest. 



The common birch (Betula pubescens and B. verrucosa) is a tree 

 making strong demands for light, as is indicated by its loose, open crown. 

 It can grow on very diverse kinds of soil : in clefts of rocks, on dry gravel 

 or sand, on moist humus, even on wet, boggy soil. The flora growing on 

 the ground in birch-forest varies widely with the nature of the soil, and is 

 often very rich because plenty of light reaches it. In some cases grass 

 forms a continuous covering over the soil. In other cases the vegetation 

 forms a kind of heath with a dense growth of Cladonia rangiferina, Poly- 

 trichum juniperum and other mosses, Molinia coerulea, Salix repens, 

 Calluna, species of Carex, and others (Grabner's ' birch-heath '). 



The birch is often accompanied by Pinus sylvestris, also often by 

 Populus tremula and Salix. The first case illustrates the difficulty of 

 grouping communities into those of xerophytes, mesophytes, and so 

 forth ; for the evergreen xerophyte grows side by side with the meso- 

 phyte. 



1 P. E. Muller, 1878, 1884, 18870, 1894. 



