221 



the first three or four species named, are those that demand in their youth an unprepared 

 soil, shade for their proper developments, the others in their sequence are placed according 

 to their capacity of sustaining shade, the latter absolutely requiring direct light for their 

 -development. 



The series is : — 



Spruce (Abies pectinata, (&c.) — Fir [Pinus ahies L.) equivalent to P. balsamea. 

 Beech [Fagus sylvatica L.) — Pinus austriaca (m^rricaws). Chestnut [C astanea vesca) 

 — Hornbeam (Carpinus Betulus). 



Ash {Fraxinus excelsior L). 



Oak {Quercus robui-), practically only one species in Germany against fourteen in the 

 United States. 



Maple (Acer campestre and 2^seudoplatanus) — Alder (Alnus glutinosa and incana). 



White Pine (Pinus strobus). 



Common Pine (Pinus sylvestris). 



Elm (Ulmtts campestris). 



Birch (Betula alba) — Aspen (Populus tretmda) — Larch (Larix eurojmea). The first 

 three can {in Germany in unprepared forest soil) not be forwarded without the protection 

 of nurse trees. In nurseries, and where the preparation of soil favours a stronger develop- 

 ment of the roots, and the capacity of the soil to absorb moisture from the air is 

 heightened, plantations prosper without shade ; so they sometimes succeed in mountainous 

 regions with frequent mists and cloudy sky, yet according to good authorities, nine out 

 of ten plantations fail even there. 



The fact, that on a loose and sufficiently "fresh" soil the young growth of these 

 species makes less demand on the shady protection of their nurses than in drier localities, 

 <;onfirms only this theory of the correlation of light, vegetation and humidity of soil. 



The hornbeam, ash, and oak, and here we may add the American chestnut, will go 

 to seed under the overshadowing mother trees, but soon the vitality of the young plants 

 will be impaired, and if, with their increasing growth, the supply of light is not granted 

 in proportion they weaken and die. Here again a humid soil will help to sustain life 

 longer, by producing a larger amount of leaves, i.e., increasing the area of evaporation. 



The species named towards the end of the list demand at an increasing ratio the in- 

 fluence of direct light for their development, the larch, above all, finding it almost impos- 

 sible to exist, where it is shut out from a i)erfect enjoyment of light. 



That the American forest trees make in this particular case an exception, nobody 

 will maintain, and there is no doubt, that they can be similarly grouped as to their relation 

 towards light and shade. 



May we not here perhaps find a clue to the change of species or rotation, in the agri- 

 cultural sense of the word, which has been observed in this country 1 Is it not the human 

 hand which has produced indirectly this change, by destroying the conditions propitious 

 for the one species and favouring those necessary for another by removing the shade of 

 nurses, which the existing species needed for its youthful life, and thus creating a growth 

 of species that are more able to develop under the direct rays of the sun 1 Has not per- 

 haps the indiscriminate denudation, giving access to the scorching sun and drying winds, re- 

 duced the humidity of the soil so far as to exclude the existing species from satisfying its 

 greater demand for moisture 1 



In changing other conditions of growth too such alternations of species are natural. 

 Bemoving the valuable timber before the seed was dropped will invariably give prepon- 

 derance to the quick-growing mostly less valuable kinds, which bear seed every year, and 

 whose light seeds are carried over large distances by winds, insects, etc. 



We will not dwell on this theme, which has so unfortunately drawn the attention of 

 the cisatlantic foresters in the wrong direction, and only once more lay stress on the con- 

 sideration, that no chemical condition but the physical conditions of forest-growth are un- 

 derlying the noted alternation of species ; species, that with regard to climate and soil are 



