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readily wherever soil and climate are favorable, but it is accomplished just 

 as surely, though infinitely more slowly, in unfavorable situations. On the 

 naked rock, the coarse detritus and gravel beds, on the purely siliceous 

 sand deposits of rivers and oceans, or in the hot, dry plains, the preliminarv 

 pioneer work of the lower vegetation is required. Algae, lichens, mosses, 

 grasses, herbs and shrubs must precede, to cultivate the naked rock, to mel- 

 low the rough gravel beds, to make the soil, to increase the soil moisture bv 

 shading the ground and gradually render it fit for the abode of the forest 

 monarch. The army of soil makers and soil breakers, the pioneers, as it 

 were, of the forest, are a hardy race, making less demand for their support 



MUIK GLACIER FOREST. 



than those who are to follow. They come from different tribes, according 

 to the climatic conditions in which they have to combat. As soon as they 

 have established themselves, they begin their cultivatory activity, which 

 consists in withdrawing from the rock or soil and from the air the nutri- 

 tive elements, returning them to the soil when they die and decay in a form 

 much more suitable for the support of the higher plants. Not only are 

 thus, by the repeated growth and decay of these pioneers, the nutritive ele- 

 ments of the soil improved and augmented, but also the physical properties ; 

 the soil is deepened and becomes mellow and its capacity" for moisture in- 

 creases. The waters, charged with carbonic acid derived from the decay 

 of the vegetable humus, hasten the decomposition of the underlying rock. 



