CHAP, xcii DECIDUOUS DICOTYLOUS FOREST 333 



sylvatica, species of Circaea, Paris quadrifolia, Convallaria majalis, species 

 of Polygonatum, Cephalanthera, Epipactis, Listera ovata, Melica uniflora, 

 also the saprophytes Neottia, Corallorrhiza, Epipogum, Limodorum, and 

 Monotropa, the last of which has roots that emit shoots. 



Shoots that travel above ground are possessed by Glechoma hederacea, 

 Lysimachia nemorum, Lamium Galeobdolon, and Lycopodium annotinum. 



Tubers occur on species of Corydalis, Arum maculatum, Cyclamen (for 

 example, in beech-forest on the Alps), Phyteuma spicatum, species of 

 Orchis, and Ophrydeae. 



Bulbs present themselves on Gagea, Allium ursinum, Lilium Martagon, 

 Galanthus, and Scilla bifolia. 



Plants that are confined to their point of fixation are : Campanula 

 Trachelium, Epilobium montanum, Sanicula europaea, Hieracium muro- 

 rum, Pulmonaria officinalis, species of Primula, Actaea spicata, Brachy- 

 podium spicatum, Festuca gigantea, Luzula pilosa, Aspidium Filix-mas, 

 A. spinulosum, and Athyrium Filix-femina. 



Lichens do not occur. 



(b) Beech-forest upon a soil with sour humus has an entirely different 

 vegetation (P. E. Miiller's trientale-vegetation J ) on the ground. Fortu- 

 nately such beech-forest is of restricted occurrence, excepting where it is 

 exposed to conversion into heath. The firm soil is permeated with roots 

 and fungal hyphae and the volume of its pores is relatively small ; not 

 being excavated nor consequently aerated by earthworms it produces 

 humous acids ; 2 moreover, it is dried up by the sun's rays, and its leaf- 

 covering is often soon blown away. On it usually flourishes a dense 

 vegetation of Aira flexuosa, a setose-leaved, xerophytic grass producing 

 compact soft tufts ; in addition there are Trientalis europaea, Maianthe- 

 mum Bifolium, the hemiparasitic Melampyrum pratense (the two last- 

 named also occur on mild humus), and a rich vegetation of mosses. The 

 close, soft mossy carpet consists of Polytrichum formosum, Hypnum 

 Schreberi, H. cupressiforme, H. purum, Hylocomium triquetrum, H. splen- 

 dens, Dicranum scoparium, Leucobryum glaucum, species of Mnium, 

 and other species ; Sphagna may also, but only rarely, be found on the 

 frequently wet, somewhat marshy soil. Calluna and Vaccinium Myrtillus 

 are often present, and thus the soil approaches that of ling-heath. 



With the way thus paved, natural regeneration of the beech is no 

 longer possible, the beech-forest ultimately disappears in many places, 

 and is replaced by ling-heath. 3 



The northern limit of beech-forest continues from the south of Norway, 

 through eastern Prussia to the Caucasus ; the companion-plants of the 

 beech, of course, vary with the locality. 



Oak-forest. 



The common oak (Quercus pedunculata and Q. sessiliflora) is a tree 

 making moderate demands in regard to light, has quincuncial phyllotaxis, 

 and shows somewhat irregular branching. Its tortuous branches give rise 

 to a crown that is neither so dense nor so shady as that of the beech. 

 In Denmark the beech suppresses the oak, because, among other reasons, 



1 P. E. Miiller, 1878, 1884, 18870, 1894. ! See pp. 62, 78. 



3 P. E. Miiller, loc. cit. ; Grabner, 1895, 1901. 



