278 FORESTRY IN FRANCE. 



Or, separating the broad-leaved and the coniferous forests from those which consist of a 

 mixture of the two, we have — 



Per cent. 



Broad-leaved forests, pure and mixed 67 



Coniferous forests, pure and mixed 15 



Broad leaved and coniferous forests 18 



The state forests show a smaller proportion of pure crops than are found in those of the 

 communes, but they also comprise a very much larger proportion of forests in which the crop 

 consists of a mixture of broad-leaved and coniferous species. The first of these differences is due 

 to the circumstance that a mixture, which is always desirable from cultural considerations, has 

 been systematically maintained in the state forests from a remote period, whereas this has not 

 always been the case in the commuiies. The second difference is chiefly accounted for by the 

 fact that those parts of the state broad-leaved forests, where, from various causes, the soil has 

 become much deteriorated, have frequently been planted up with conifers, which are tlie only 

 kinds likely, on account of their capacity to grow on poor soil, to succeed under such condi- 

 tions; but these are in such cases, only intended to act as nurses to broad-leaved species, 

 which are subsequently to be raised under their shelter. But little work of this kind has yet 

 been accomplished in the communal forests from want of the needful funds. The private 

 forests resemble those of the communes rather than those which are state property, but a fur- 

 ther comparison in this respect between them and the other classes of forests need not be 

 made at present. 



Many circumstances combine together to influence the nature of the vegetable growth, 

 which characterizes any particular locality. Thus, a "limestone soil," which is one contain- 

 ing more than four or five per cent, of carbonate of lime, is usually marked by a rich and 

 varied vegetation ; while on a silicious soil the flora is much more simple and uniform, the 

 undergrowth being often formed of bilberry [yaccinium mvrtillus), broom and heather. 

 Forty-four per cent, of the French forests are on limestone. But the principal forest trees are 

 not much affected by the chemical composition of the soil, the two deciduous oaks, the 

 beech, the hornbeam, silver fir, spruce fir, the larch, being classed as " indifferent" to it. The 

 evergreen oak, however, shows a preference for limestone; and the Scotch pine flourishes best 

 on a silicious soil; but the maritime pine will not grow on limestone. The climate, which 

 varies with the latitude, altitude, amount and distribution of the rainful, proximity, or other- 

 wise of the sea, and other conditions, is the principal factor in determining the distribution of 

 trees, each of which finds its home in the locality which best suits its temperament. The hot 

 region of the south, the temperate regions of the north and center, and the mountains, are 

 each characterized by the spontaneous vegetation to which they are adapted. Thus, in the 

 south, are found the evergreen oak and the maritime pine ; while the spruce, the silver fir, 

 and the larch inhabit the mountains; and the five other species mentioned, grow chiefly in the 

 temperate region. The physical condition of the soil also exercises an important influence on 

 the growth and local distribution of trees; for example, quercus pedunculala, and the horn- 

 beam, will grow on moist soil, which does not suit either guerais sessilifiora, the beech, or 

 the evergreen oak. 



During the entire course of their development, trees of all kinds require light; but during 

 the early stages of their existence, some of them must be completely in the open, without any 

 cover at all ; while for others, various degrees of shade are necessary. This quality of the 

 young plants is, generally speaking, in direct relation to the abundance of the foliage of the 

 adult tree from which they spring. Those which, when young, require much light, such as 

 the larch, the pines, and the oaks, are called the " robust," or trees of light cover, while 

 others, which will not stand exposure, such as the beech and silver fir, are called " delicate," 

 or trees of heavy cover. The spruce and the hornbeam are classed intermediately between 

 kinds of light and heavy cover. This is a very important question to the forester, not only 

 with reference to the method to be adopted for raising a crop of any particular kind of trees. 



