AMOUNT PRODUCED. 593 



closely. Oaks, black poplar and ash come some way behind the 

 last group ; Scotch pine and larch produce still less foliage, 

 whilst birch and aspen close the list. 



The duration of the leaves on the trees is evidently longest 

 for evergreen conifers, silver-fir, spruce and pines. In the 

 case of the black, Weymouth and Scotch pines, the needles 

 remain from two to four years ; in the spruce and silver-fir, four 

 to six years and even longer for the latter. Hence it follows 

 that pines shed about one-third of their foliage annually, the 

 spruce and silver-fir only the fifth or sixth part. These species, 

 therefore, are much worse producers of litter than follows from 

 the density of their foliage. 



Silver-fir, spruce and beech possess in the highest degree the 

 property of growing in densely stocked woods, next come the 

 hornbeam and hazel — some way further down in the list — alder 

 and sycamore. In the case of ash, elms, oaks, sweet chestnut, 

 birch, aspen, Scotch pine and larch, the woods open out much 

 earlier. As compared with woods of light-demanding trees, those 

 of mixed light-demanders and shade-bearers produce more litter, 

 whilst woods of spruce, silver-fir and beech produce litter most 

 abundantly. 



(b) Locality. — The nature of the locality in which it is grown 

 has the greatest possible influence on the well-being of a species 

 of tree. The more a locality suits a tree, the greater, other 

 conditions being equal, will be the production of litter. As a 

 rule, a moist atmosphere, provided there is sufficient heat avail- 

 able for the species in question and a rich soil, increases the 

 density of the foliage. 



Localities with high relative atmospheric humidity produce a 

 much denser leaf-canopy than those where the air is dry ; the 

 spruce in high mountain-regions, the beech in extensive wood- 

 lands, the hornbeam, alder and birch in damp lowlands near 

 the Baltic, produce much more foliage than the same trees in 

 other localities. The better the soil, the deeper and denser 

 the leaf-canopy ; but the soil and local climate must always be 

 considered together. The aspect is also influential, as owing 

 to their greater moisture, north and east aspects produce as a 

 rule most litter. R. Weber's* note on beech leaf-production 



* Ebermayer, Die Waldstreu, p. 37. 

 VOL. V. Q Q 



