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THE GREENWOOD TREE. 



whose aid to digest it. The carbon alone is no good 

 to the tree if it can't get sometliing which will separate 

 it from the oxygen, locked in close embrace with it. 

 That thing is sunshine. There is nothing, therefore, for 

 which herbs, trees, and shrubs compete more eagerly 

 than for their fair share of solar energy. In their 

 anxiety for this they jostle one another down most 

 mercilessly, in the native condition, grasses struggling up 

 with their hollow stems above the prone low herbs, 

 shrubs overtopping the grasses in turn, and trees once 

 more killing out the overshadowed undershrubs. One 

 must remember that wherever nature has free play, 

 instead of being controlled by the hand of man, dense 

 forest covers every acre of ground where the soil is deep 

 enough ; gorse, whins, and heather, or their equivalents 

 grow wherever the forest fails ; and herbs can only hold 

 their own in the rare intervals where these domineering 

 lords of the vegetable creation can find no foothold. 

 Meadows or prairies occur nowhere in nature, except in 

 places where the liability to destructive fires over wide 

 areas together crushes out forest trees, or else where 

 goats, bison, deer, and other large herbivores browse 

 them ceaselessly down in the stage of seedlings. 

 Competition for sunlight is thus even keener perhaps 

 than competition for foodstuffs. Alike on trees, shrubs, 

 and herbs, accordingly the arrangement of the leaves is 

 always exactly calculated so as to allow the largest 

 possible horizontal surface, and the greatest exposure of 

 the blade to the open sunshine. In trees this arrange- 

 ment can often be very well observed, all the leaves 

 being placed at the extremities of the branches, and 



