36 THE AFFORESTATION OF SURPLUS LAND. 



in alternate lines, or whether each species is to form separate 

 groups, depends on circumstances, especially the relative height 

 growth, and the shapes of the species in mixture. Where these 

 differ, groups are indicated, a system which has of late years 

 much grown in favour with foresters. At any rate, the species 

 should he placed into alternate lines, so that one can be 

 protected against the other. 



3. The Density of Forest Crops.* 



In the previous section special attention has been drawn to 

 the necessity of growing a forest crop so that the fertility of 

 the soil is preserved, if not increased, and that the most valu- 

 able class of timber is produced. The question may therefore 

 be asked, " What is the proper density of a forest crop? " or 

 to put it differently, " What is the most suitable growing space 

 to be given to each tree ? " 



The theory of the case is simple enough, and it runs as 

 follows : " The density of a forest crop should le such that the 

 objects u'ltieli the proprietor has in rieir are most fully realised." 

 Hence, if the object is to produce landscape beauty, it is in 

 some cases desirable to give to each individual tree sufficient 

 space to grow and spread in a natural way, while in others a 

 group of massed trees may be desirable ; no special law can be 

 laid down in this case. 



When trees are grown for economic purposes, matters are 

 different. Here a balance must be struck between the preser- 

 vation of the fertility of the soil and the production of high- 

 class timber. For the former purpose it is best to keep the 

 crop as dense as possible from start to finish ; but such a pro- 

 cedure may seriously interfere with the second object, and it 

 may involve heavy additional expenditure at starting. 



In the case of natural regeneration, successfully carried 

 through, as many as 50,000 or 100,000 seedlings may be found 

 on an acre, and these are, after a comparatively short space of 



* See " Manual of Forestry," Vol. II., third edition, pages 140, 174. and 289. 



