CHAP. VI.] 



The Food of Trees 



77 



As, however, the normal density of foliage, natural to the different 

 kinds of woodland trees, varies greatly with each species, and also for 

 one and the same species of tree according to the nature of the soil, the 

 age and the method of treatment of the crop, and various other factors 

 of sylvicultural importance, these data, which are by no means complete 

 or intended to be advanced as finally authoritative, are rather of theo- 

 retical interest than of practical sylvicultural value. When investigating 

 the actual quantity of water required by the Beech for normal transpira- 

 tion annually, von HOnel estimated that 

 A Beech tree 35 years of age 



consumed per diem i kilo.= 2-204 Ibs. = 0-220 gals, of water. 



A Beech tree 50-60 years of 



age consumed per diem ... 10 kilos. = 22-040 Ibs. = 2-204 gals, of water. 

 A Beech tree 115 years of age 



consumed per diem 50 kilos. = i 10-200 Ibs. = n.O2Ogals. of water. 



Computing the average number of trees per acre, he arrived at the 

 following results : 



But it should be remembered that the quantity of soil-moisture 

 requisite for transpiration through the foliage must be very considerably 



