Chap. X] EDAPHIC INFLUENCES IN TEMPERATE ZONES 659 



The characteristic plant of high-moor is the Sphagnum (Fig. 399), in 

 Germany and Switzerland Sphagnum cymbifolium (Fig. 400), the spongy, 

 water-absorbing cushions of which gradually grow in height, whilst their 

 lower parts pass over into sphagnum-peat. This upward growth causes 

 the moor to raise itself steadily above the level of the subterranean water, 

 specially in its centre, which corresponds to the older part of the moor. 

 The somewhat slight convexity of sphagnum-moor — the centre may be as 

 much as four meters higher than the edge — has led to the appellation of high- 

 moor. In virtue of the water-absorbing power of the cushions of Sphagnum 

 even the highest parts of the moor remain permanently saturated with water. 



Absorption of water by the Sphagnum is partly internal, through the agency ot 

 capillary cell-cavities (Fig. 400), and partly external, in the coarse capillaries between 

 the leaves : the first method is the normal one in most of the high-moor Sphagna, 

 and is rendered highly efficient by the very complete capillary system inside the 

 axes and leaves. The cortex of the stem and the leaves in all Sphagna consist of two 

 elements, namely, cells containing chlorophyll and chambers without protoplasm. 

 The latter, which, like the tracheae of higher plants, are usually stiffened by fibrous 

 thickenings, communicate uninterruptedly with one another and with the exterior 

 by means of round openings, and form a system of continuous capillary tubes, by 

 which the water obtained from the medium is rapidly conveyed to the most remote 

 parts of the plant. 



In Sphagnum cymbifolium and its allies, the superficial cells of the cortex are 

 provided with numerous pores opening outwards, and below they also communicate 

 by openings larger than in other species, in which the hyaline cell-lumina serve more 

 for storing water than for conveying it. The movement of water, according to 

 Oltmanns, takes place in S. cymbifolium, partly and indeed chiefly in the cortex of the 

 stem, partly through the leaves, the capillary interspaces between which accomplish 

 the passage of water from one leaf to the next above it. In other species of 

 Sphagnum the coarse method of suction in the external capillaries between the leaves 

 is more efficient. 



A leaf-structure and a movement of water similar to those in S. cymbifolium, the 

 latter however only in the leaves, is repeated by another moss common in peat- 

 moors, Leucobryum glaucum, which is remote systematically but agrees in its mode 

 of life. It is not however confined to peat-moors, but occurs in other wet stations 

 that are free from lime. 



In other respects the flora of high-moors is composed partly of species of 

 plants that occur also in dry stations without peat ; thus in Germany, there 

 are Calluna vulgaris, Vaccinium Vitis-Idaea, Betula pubescens ; partly of 

 plants that also occur on meadow-moors, such as Drosera rotundifolia and D. 

 longifolia, Polygala uliginosa, Comarum palustre, Pedicularis palustris, Salix 

 repens, species of Eriophorum, many species of Carex ; and partly of species 

 or varieties that are characteristic of high- moors, such as Pinus montana, var. 

 uncinata, Drosera obovata and D. intermedia, Viola palustris, Vaccinium 

 Oxycoccos, Andromeda polifolia, Betula nana, Rhynchospora alba. 



U U 2 



