660 ZONES AND REGIONS [Pt. Ill, Sect. II 



The vegetation of meadow-moor displays a greater number of species of 

 plants that occur in other stations than does that of high-moor, and this is 

 probably owing to the meadow-moor having a smaller quantity of organic 

 substances in solution and a larger quantity of mineral substances. The 

 meadow-moor, nevertheless, also possesses its characteristic species ; thus, 

 according to Sendtner, in Bavaria there are Epilobium palustre and E. 

 tetragonum, Senecio aquaticus and S. paludosus, Gentiana Pneumonanthe, 

 Gratiola officinalis, J uncus conglomeratus, Rhynchospora fusca, several 

 species of Carex. 



To what extent the characteristic moor-plants require the organic com- 

 ponents of acid humus, or are confined to it only because like halophytes 

 they can endure it and, owing to the consequently reduced competition 

 with other species, are able to maintain their position, is still an open 

 question in many cases. Yet it has been proved that several typical moor- 

 plants, specially some belonging to meadow-moor, can thrive when culti- 

 vated on ordinary soil, as, for instance, Gratiola and Epilobium. 



That there is a consumption of humus in the nutrition of certain species 

 of the moor-flora may with great probability be assumed from the fact that 

 in many of them (Ericaceae, Empetrum, Orchideae) the endotrophic myco- 

 rhiza has been demonstrated. Yet the assimilation of humus in moorland 

 soil appears to be much more difficult even for fungi than on mild humus 

 soil, inasmuch as the large saprophytic fungi that appear in such abundance 

 on mild humus are entirely absent from moors. 



In another respect moor, especially thick high-moor, affords conditions 

 unfavourable to plant-life, namely in its poverty in mineral substances — owing 

 to the great distance of the vegetation from the mineral substratum and 

 to the absorptive influence of humus — which renders it difficult or 

 impossible for the plants to obtain soluble salts. In the earthy layer of 

 humus, which covers high-moor to a thickness of two to three and a half feet, 

 the proportion of the organic to the inorganic components is about 5 : 2, 

 whereas in good humus soil it sinks to about 1 : 2. The layer of peat on 

 meadow-moor is thinner and much richer in mineral matter than that of 

 high-moor, where its thickness in the centre may amount to thirty feet. 



Moor, in particular high-moor, is also among the poorest of soils as 

 regards content of assimilable nitrogenous substances. Nitrogen indeed is 

 very abundant, but in the intractable form of humified albuminous bodies. 

 Nitrifying bacteria are rare owing to the poverty in oxygen, and the bacte- 

 rium of the leguminous tubercles does not thrive in peat-moor. 



Many moor-plants, particularly in the American flora, to a certain 

 extent compensate for the above-mentioned disadvantages by becoming 

 carnivorous plants that digest animal food and thus utilize small animals. 



Familiar on European moors is the occurrence of luxuriant patches of 

 Drosera, in places where little or no vegetation otherwise thrives. Pingui- 



