CHAP, in.] Characteristics of Trees 65 



and White Alder. But Willow, Chestnut and Elm at the same 

 time throw out a very fair proportion of stoles, which may 

 be cut away and transplanted like seedling growth. 



VII. Differences as to Attainment of Maturity and 

 normal Duration of healthy Growth. 



The ages to which the various kinds of forest trees may 

 be grown in a healthy condition without showing visible signs 

 of senile decay exhibit great differences. Thus we find Oak 

 and Scots Elm attaining 500 years and more, English Elm, 

 Silver Fir and Beech 300-400 years, Ash, Maple, Sycamore, 

 Spruce, Larch, Scots Pine and Hornbeam about 200 years, 

 whilst Aspen, Birch, Alder and Willow seldom attain over 

 100 years. Indeed, many historical trees are known to be 

 very much older than any of these limits ; but even the above 

 ages are far in excess of any rotations that could possibly be 

 maintained in woodlands worked on sound economic sylvi- 

 cultural and financial principles. 



For the attainment of healthy old age the essential con- 

 ditions are (i) that the opportunities of growth must be such 

 as to permit of the normal development of all the organs of 

 nourishment, and (2) that the soil and situation must continue 

 to supply all demands as to warmth, moisture, &c., made by 

 the individual species. But very frequently the economic re- 

 quirements of sylviculture are incompatible with the demands 

 as to growing-space, &c., that are involved in the above. And 

 the capacity of different genera for regaining normal vigour, 

 after being first grown for a long time in close canopy and 

 later on allowed a larger measure of light and air, varies con- 

 siderably ; it is greatest in Oak, Lime, Willow, Elm and Silver 

 Fir, and least in Alder, Aspen, Maple, Sycamore, Beech, Horn- 

 beam, and Spruce. 



From the practical sylvicultural point of view, the following 

 may be regarded as the ordinary average limits of age which 



F 



