36 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



5 per cent of lime, and in the fourth class only 0*4 per cent. 



The quantity of phosphates has also a marked influence; but 

 the proportion of magnesia and potash seems to remain fairly 

 constant, the poorest " locality class " being nearly as well 

 provided in respect of these as the most productive. 



Composition of the Forest. 



At present about two-thirds of the forest consists of broad- 

 leaved trees, and a hundred years ago these hardwoods occurred 

 to the extent of 90 per cent. But it was not always so ; in 

 the Middle Ages the Sihlwald was practically a coniferous forest. 

 At that time, as the investigations of the Forstmeister have 

 proved, fir and pine timbers were those most desired by the 

 inhabitants of the district, who used the wood for fencing 

 purposes and house-building. Later, when stone came more 

 largely into use in the construction of dwelling-houses, and 

 the population increased, more timber was required for fuel. 

 Attention was then turned more to the beech, along with 

 other broad-leaved trees, and a rotation of 80 to 100 years 

 was instituted. No doubt, too, more enlightened methods of 

 silviculture had something to do with the change, for the 

 beech was needed to improve the fertility of the soil. In this 

 connection Herr Meister makes the interesting remark that 

 where light-demanding conifers predominate, the soil has 

 certainly been impoverished, and that it is no longer of 

 sufficient strength for the growth of hardwoods. Moreover, 

 the fact has been noted that communal or other forests, well 

 managed on co-operative lines, are largely beech forests, 

 whereas the more neglected and comparatively poorly treated 

 private woods bear coniferous species. Of course one must 

 not push this generalisation too far, because, as we all know, 

 a well managed forest of evergreen conifers can, and does, 

 fully maintain productivity. In fact, the tendency in the 

 Sihlwald to-day is to increase the proportion of softwoods, 

 particularly silver fir; but it is interesting to observe the high 

 esteem in which beech is held by Continental foresters. 



The beech is by far the commonest tree in the Ziirich woods. 

 Occupying an important place along with it are ash, sycamore, 

 maple, and Wych elm. Room is also found for the hornbeam 

 and common alder, birch, aspen, and willow ; but the last 



