. The ecological relations of roots . ing root habit of their predecessors of thegravel-slide, this is supplemented by a much deeper portion whichextracts water and nutrients below the 18-inch level, as well as verylargely from the second and third foot of soil. The surface-spreadingroots may be explained by the frequent mountain showers whichsupply water rather continuously to the shallow soils, while thedeeper-seated ones reflect the better deep-soil conditions, but especiallythe more intense competition for water of this denser thick surface layer of loose rock fragments of t
. The ecological relations of roots . ing root habit of their predecessors of thegravel-slide, this is supplemented by a much deeper portion whichextracts water and nutrients below the 18-inch level, as well as verylargely from the second and third foot of soil. The surface-spreadingroots may be explained by the frequent mountain showers whichsupply water rather continuously to the shallow soils, while thedeeper-seated ones reflect the better deep-soil conditions, but especiallythe more intense competition for water of this denser thick surface layer of loose rock fragments of the gravel-slide hashere become more disintegrated and closely packed, and soon givesway to soil. Hence water evaporates more freely. This, with thecompetition of the taller half-gravel-slide plants, accounts for thedisappearance of gravel-slide species. The former shade those oflesser height, but especially compete with them for water, undoubtedlyrelying upon their deeper penetrating roots during periods of drought. PLATE B S C E H B. le front of thefmus triticoides,j; H, Heuchera
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Keywords: ., bookcentury1900, bookdecade1910, bookidecologicalre, bookyear1919
