BRITISH FOREST TREES 297 



stem. From insects it suffers comparatively little, although, 

 like the common alder v its roots are exposed to damage 

 from the larvae of species of Melolontha, and its wood in the 

 thicket and pole stages of growth to injury by the larva 

 of Cryptorhynchus lapathi ; this latter also feeds on the 

 foliage as a perfect insect. 



Sylvicultural Treatment of White Alder. Although closely 

 resembling the common alder in many respects, this species 

 shows marked differences in others ; it is no denizen of the 

 marshy soils, and does not naturally form pure forest, but 

 prefers rather the fresh, mellow soil to be found in the 

 vicinity of brooks and streams, and in narrow valleys, where 

 it usually occurs in patches or small groups that have arisen 

 from stoles flushed by the roots of a parent tree. This 

 capacity of throwing up a wealth of rapidly developing root- 

 suckers is a marked characteristic in which it differs essentially 

 from the common alder, whilst, as regards power of bearing 

 shade, it also has some little advantage over this species. 

 They are nearly alike as regards rapidity in growth and 

 development, and in general reproductive capacity, but on 

 the less moist soils preferred by the white alder this power 

 is not so long retained. Like the common species it is only 

 treated as coppice, and worked with a rotation varying 

 generally from ten to thirty, but not exceeding thirty to 

 forty years. Where there is any demand for its soft timber, 

 it is well adapted for the underplanting of standards of oak, 

 ash, maple, &c., in order to protect and improve the soil 

 when these have completed their growth in height and have 

 become interrupted in canopy ; it can there be harvested 

 several times before being so weakened in reproductive 

 power by the shade of the standards as to be suppressed. 

 For the planting up of stony soil through which a supply of 

 water trickles slowly, this species is of great value as paving 

 the way for a growth of grass, to better accumulation of soil, 



