CHAP, xcn DECIDUOUS DICOTYLOUS FOREST 331 



of vegetation. The number and nature of the plants associated with 

 definite trees varies with the amount of shade that these cast : but this 

 is more fully discussed in the sequel. 



Herbs on the floor of the forest are mostly tall and possessed of 

 elongated internodes : they are not rosette-plants. The leaves of plants 

 forming the underwood and vegetation on the ground are similar to those of 

 the trees forming the high-forest, but are thinner and still less xerophytic ; 

 some are definitely sciophylls, whose structure approaches that of a hydro- 

 phyll. This is mainly due to shade and a moist atmosphere, but possibly 

 also to the damp humus-soil. The leaves are therefore generally large, 

 broad, flat, thin, unpolished, and glabrous for instance, in Oxalis Aceto- 

 sella, Anemone nemorosa, Impatiens Noli-me-tangere, Lactuca muralis, 

 species of Corydalis, Circaea, Paris, Adoxa, Mercurialis, and Convallaria. 

 Grasses of the forest have broad, flexible, mostly arcuate leaves, which 

 are devoid of any power of rolling up, and bear unprotected stomata on 

 both faces or largely on the upper face ; as examples may be mentioned 

 Milium effusum, Poa nemoralis, Melica uniflora, M. nutans, Dactylis 

 glomerata, Festuca gigantea, Bromus erectus, and Brachypodium sylva- 

 ticum. 



Many plants in moist shady forest are, according to Wiesner, 1 ombro- 

 phobous, and it is impossible to wet the surfaces of their leaves; but 

 others, including Sanicula europaea, are ombrophilous. 



Epiphytes are represented mainly by mosses and lichens, never by 

 Spermophyta definitely adapted to an epiphytic mode of life. Of lianes 

 there are but few Lonicera Periclymenum, Hedera, Humulus, and 

 Clematis. 



The soil of the forest entertains many saprophytes, including fungi 

 that show themselves especially in the autumn of moist years. Among 

 Spermophyta there are only a few holosaprophytes Monotropa, Neottia, 

 Epipogum, and Corallorrhiza but probably many hemisaprophytes, 

 including Orchidaceae and species of Pyrola. Mycorhiza occurs in con- 

 nexion with many trees and with saprophytes. 



ASSOCIATIONS 



As examples of associations belonging to dicotylous forest in temperate 

 countries, we may mention beech-forest, oak-forest, and birch-forest. 



Beech-Forest. 



Beech-forest is most luxuriantly developed in Denmark and in the 

 west of Germany on humus-soil. Fagus sylvatica, the beech, is very 

 definitely a shade-enduring tree ; its tall, slender, smooth, light-grey 

 trunk bears a crown that is rendered dense and shady by the distichous 

 phyllotaxis, the numerous dwarf-shoots, the mosaic of leaves, and by 

 the power possessed by the leaves of assimilating in weak light. The light 

 reaching the ground is very subdued, for which reason there is no under- 

 wood, and the ground in many beech-forests is extremely poor in plants 

 a result that is also partly due to the thick carpet of fallen foliage. 



' See p. 32. 



