CHARACTEBISTICS OP AN AUXILIARY SPECIES. 331 



4. It must be able to thrive in the same soil as the principal 

 species. This is a truism, 



5. It must possess a different ramification of branches and roots 

 from that of the principal species. In other words, it ought to be 

 able at once to occupy or fill up space in the soil and in the leaf- 

 canopy, which the principal species cannot profitably utilise ; and 

 it must be able to do this without tending to invade or strangle the 

 crowns and root-apparatus of the latter, 



6. Its stature must not be less than the minimum length of bole 

 demanded from the principal species. -In no other way, save very 

 exceptionally, could tlu's length of bole be produced, and, at the 

 same time, the leaf-canopy maintained in a complete state. 



7. If natural regeneration by seed is sought, the auxiliary species 

 should be able to reproduce itself spontaneously and readily by seed 



from a few seed-bearers only ; and if the regeneration is to be effected 

 artificially, its propagation by means of sowing or planting, or both, 

 ought to be easy and inexpensive. In coppices the auxiliary species 

 should be able to coppice vigorously beyond the close of the longest pos- 

 sible rotation, but it should not be able to produce abundant suckers. 

 It stands to reason that as a crop ages, the relative proportion of 

 the most valuable and hence principal species ought to be increased 

 to the farthest limit compatible with their favourable growth. 

 Hence we must be able to effect the natural regeneration by seed of 

 the auxiliary species with the help of as few individuals of it as pos- 

 sible. In the case of coppices the auxiliary species should not be- 

 come invasive by a too abundant production of root-suckers. 



8. Its longevity ought to be at least equal to the term required for 

 the trees of the principal species to attain their full length of bole. 

 Otherwise after the death of the trees of the auxiliary species, 

 none could be produced for years to take their place, and in the 

 meantime the absence of companions to help in drawing them up 

 and in pruning their boles naturally would affect detrimentally the 

 longitudinal growth of the trees of the principal species. 



The preceding is a complete enumeration of the essential charac- 

 teristics of an auxiliary species ; it remains now briefly to mention 

 the non-essential, though still useful and desirable, characters of the 

 same. They are - 



1. Rate of upioard growth, until the high-pole stage is reached, 

 somewhat sloiver than that of the principal species. In other words, 

 it is desirable that, provided the auxiliary species is not required 

 as a nurse, it should at no stage of growth be able to rise up on a 



