ELEMENTARY FORESTRY 383 



are of interest in connection with all the foregoing work in 

 gardening and the cultivation of plants, for water, in con- 

 nection with rich soil, is the great essential to plant growth. 



Let us take again 100 grams of gravel, sand, soil from 

 the barren field, rich loam from the woods, leaf mould, and 

 25 grams of dry pulverized leaves. Knock the bottoms 

 out of six tall, slender bottles (the common olive-oil bottles 

 are well adapted for this experiment, or large glass tubes 

 may be used). Dry before weighing and put the samples 

 each into its bottle, inverted, with the neck stoppered with 

 a notched cork. Shake the different materials so that 

 they lie evenly and compactly, and then from a measuring 

 glass pour in water slowly, so that the whole mass is wet, 

 and see how much water each will absorb before the water 

 begins to run out at the bottom. Or we may pour into 

 each a known amount, say 100 cubic centimeters, and then 

 measure all that runs through. The quantity absorbed is 

 known as capillary water or film moisture. It is this that 

 constitutes the water supply for the roots of plants in the 

 soil. Fertility, the power of the soil to support plants, 

 thus depends largely upon its power to retain water. 



In the experiment represented in Fig. 154 the results 

 were as follows : 



Grams Absorbed 



Gravel 100 S.s grams 



Sand 100 36 



Barren Soil 100 40 



Rich Loam 100 69 



Leaf Mould 100 210 



Leaves 25 120 



To make the result still clearer we may take a piece 

 of punk, or partially decayed wood, dry thoroughly and 



