40 Studies in Forestry [CHAP. n. 



the stem, a larger proportion of the assimilated food is utilized 

 in the upper part of the tree than in the lower, the result is 

 that the boles are more full-wooded, i. e. they approach more 

 to the cylindrical in form, than is the case with poles growing in 

 crops below the normal density in leaf-canopy. Until the chief 

 growth in height has been completed, therefore, the mainten- 

 ance of close canopy affects not only the actual length of the 

 bole or clean stem and its shape, but also the proportion of 

 timber obtainable, as compared with branchwood ; and these 

 are matters of great technical and financial importance. 



When seedling growth or young plantations, after having 

 passed through the thicket stage of growth, develop into pole- 

 forest, and finally into tree- forest or high-timber, the crop consists 

 of various classes of growth named, according to the position 

 they may occupy in the struggle for increased growing space : 

 (i) predominating, (2) dominant, (3) dominated, and (4) sup- 

 pressed, although of course there are no hard and fast lines 

 existent between these different classes. Until far on in the 

 life-history of the crop, the predominating class comprises 

 within it all the individuals that are likely to form any portion 

 of the mature fall of timber ; hence, in all clearings and thin- 

 nings undertaken with a view to the tending of woodlands 

 a subject that will be considered later on (see Chap. IX) 

 the removal of the suppressed and, to a greater or less extent 

 (according to the species), the dominated classes, is advisable. 

 Such cultural measures are not only for the purpose of assist- 

 ing nature in the work of eliminating the individuals no 

 longer required in the maintenance of a leaf-canopy of normal 

 density, and of helping the more vigorous stems towards their 

 more rapid development, but also for removing all poles and 

 young trees of enfeebled energy and perhaps sickly growth, 

 which might offer dangerous attractions to noxious insects. 

 Compared with the total number forming the crop, the per- 

 centage of individual stems necessary for the retention of a leaf- 

 canopy of normal density varies essentially according to (i) the 



