CHAP. LXXXVI EVERGREEN CONIFERAE 313 



naria dioica, and others, also of masses of lichens (Cladonia) and mosses 

 (Grimmia). In other places different mosses (Hylocomium and Dicranum), 

 Luzula pilosa, and grasses particularly two narrow-leaved xerophytic 

 species, Aira flexuosa and Festuca ovina and some of the plants already 

 enumerated, combine to form a much closer and softer covering. These 

 different varieties of pinetum are, according to the dominant species, 

 termed pinetum cladinosum, pinetum hylocomiosum, pinetum herbidum, 

 and so forth. 



The ground-vegetation of pine-forest thus consists of xerophytes ; for 

 the soil is usually poor and dry, while light and wind can usually penetrate 

 with ease and tend to dry up the vegetation. Yet even in this forest one 

 or another kind of mesophyte can gain a footing. The pine-forests of 

 southern Russia obviously differ not a little from Scandinavian pine- 

 forest, since many tall perennial herbs rise from their soil. 



Birches are sometimes interspersed in pine-forest, as they, as well as 

 the Scots pine, are light-demanding trees. 1 



Spruce-forest. 



Picea excelsa, the common spruce or Norway spruce, thrives upon 

 various kinds of soil, as is the case with Scots pine, but is more exacting 

 in its demands, as it does not endure dryness so well ; beneath it no such 

 xerophytic vegetation grows. It is a shade-enduring tree ; the branches 

 and needles accordingly remain attached for a much longer time (the 

 needles living for eight to thirteen years) than in the case of Scots pine, 

 while the crown acquires the familiar dense conical form. The vegetation 

 clothing the ground harmonizes therewith. Underwood is wanting, and 

 the ground in the darkest spruce-forest is often quite bare, as in its close 

 carpet of needles, often several centimetres in thickness, there grow only 

 a few stunted mosses, though crowds of pileate fungi develop in autumn. 

 Where the light is stronger the mosses become more vigorous ; and in 

 good forests the ground-vegetation may combine to form a continuous, 

 close, uniform, green, soft carpet of mosses. These are mainly species of 

 Hylocomium, whose cushions lie loose above the soil and conceal humus 

 that is occupied by earthworms ; in addition there occur, among others, 

 Polytrichum and Dicranum, both of which genera have the power of 

 producing raw moss-humus. In the mossy carpet and on the loose soil 

 there are often numerous scattered Spermophyta, many of them possess- 

 ing creeping rhizomes, e. g. Oxalis Acetosella, Trientalis europaea, Circaea, 

 Vaccinium Myrtillus, V. Vitis-idaea, species of Anemone, Viola sylvatica, 

 Linnaea, and species of Pyrola (in addition to ferns and lycopods). Some 

 of these plants are pronounced sciophytes, and some, including Monotropa 

 and Goodyera, are at the same time saprophytes. For lichens spruce- 

 forest is mostly too dark, so that neither soil nor stems are densely clothed 

 with them ; yet an exception in this respect is provided by spruce-forest 

 on sterile soil and at higher altitudes, where Usnea festoons the branches 

 with its wisps and gives to the forest a characteristic appearance. 



1 A considerable literature dealing with European pine-forest exists ; the most 

 recent papers are those by Domin, 19056; G. Andersson and Hesselman, 1907; 

 A. Nilsson, 1896, 1897 a, 18976, 1902; Hesselman, 1906; S. Birger, 1904. 



