BRITISH FOREST TREES 227 



worked as high forest the fall is usually fixed between sixty to 

 eighty years ; reproduction as coppice is, however, the rule. 



Liability to Suffer from External Dangers is on the whole 

 not a plea that can be urged against a more extended 

 cultivation of the common alder. From the brittle nature 

 of its wood it is apt to have its branches snapped off by 

 heavy winds, but with its deep root-system it is little apt to 

 be thrown as windfall. Late frosts often damage the young 

 foliage, especially of coppice-shoots, but the recuperative 

 power is so great that, as a rule, the damage done is not 

 very considerable. Inundations occurring in spring to such 

 an extent as to submerge the stools, act injuriously on the 

 coppice-shoots, and also on the foliage of older alders if 

 taking place at the time of the flushing of new leaves ; 

 otherwise a temporary excess of moisture is not in general 

 followed by injurious results. On the other hand, it can 

 maintain no successful struggle against drought, and is 

 injuriously affected by loss of subsoil-moisture. 



From insects it suffers little damage on the whole, its 

 chief enemy being the larva of Cryptorhynchus lapathi, 

 which attacks the wood of young shoots and stems, whilst 

 older trees suffer from the larvae of Anobium tesselatnm and 

 Pfilinus pectinicornis, and the caterpillars of Cossus ligniperda 

 and Zeuzera aesculi ; Apoderus coryli, Rhyncites betiilae, and 

 R. betuleti, both as larvae and beetles, do noticeable damage 

 to the foliage. Nectria ditissima originates cankerous fun- 

 goid growth in the stem, whilst species of Poiyporus cause 

 red and white rot in the timber. 



Sylvicultural Treatment of the Alder. The common alder 

 is capable of forming pure forests, or the ruling species in 

 mixed forests on low-lying marshy soil where it often cm< n 

 extensive areas, but on the lower hills and uplands, and in 

 muiht valley* and patdiex or along the banks of streams, it 

 is usually limited to large groups or (lumps differing 



(,) 2 



