SECTION XVI 



CLASS XIII. MESOPHYTES 



CHAPTER LXXXVII. MESOPHYTIC VEGETATION AND 



FORMATIONS 



Mesophytes ^ are plants that show a preference for soil and air of 

 moderate humidity, and avoid soil with standing water or containing 

 a great abundance of salts. No single factor is of paramount import to 

 mesophytes. They select places where the atmospheric precipitations 

 are distributed over the seasons of the year more equably than in the 

 homes of xerophytes. In the habitats of mesophytes the soil seems 

 always to be rich in alkaline humus. 



The morphology and anatomy of mesophytes have already been 

 discussed on p. 135. In temperate regions one often finds a difficulty 

 in interpreting the adaptations shown in these plants. Many species 

 are very plastic in epharmosis ; such is the case with the beech ^ 

 and many common European plants. In their power of adjusting 

 themselves to differences in the surroundings, mesophytes perhaps exceed 

 all other plants ; but we know too little in regard to this matter. The 

 diversity of leaf-form is as a whole greater than in other formations. 

 Divided and compound leaves, also leaves with the margin indented in 

 various ways, are more common than among xerophytes. 



Compared with certain communities of xerophytes and halophytes, 

 no mesophytic community is so open or poor in plant-life ; this must be 

 ascribed to the more favourable conditions of hfe. In the humblest and 

 simplest communities grasses and other herbs play the weightiest part ; 

 among such communities are meadows and pastures. Richer than these 

 is vegetation composed of tall perennial herbs and mesophytic bushes, 

 in which several storeys of plants occur. And richest of all is tropical 

 rain-forest. 



Mesophytic communities find their homes largely within temperate 

 regions, and particularly within the northern forest-belt, where the rain 

 mainly falls in summer and autumn ; they therefore occur specially 

 in the zones of evergreen coniferous forest and of deciduous dicotylous 

 forest, but they also occur in Polar countries and within the tropics. 

 Especially in temperate regions they are often associated with cultivated 

 land ; the soil and cHmate that they require admirably suit them for 

 cultivation by man. As a result of cultivation of the soil the natural 

 communities, which beyond doubt were originally very few in number, 

 have been destroyed and broken up into a number of new communities, 

 which are largely cultivated, semi-cultivated, or ruderal in character. 



' See Chapter XXX, pp. 131, 135. * Stahl, 1880, 1883. 



