AERATION CONDITIONS IN SPHAGNUM, 39 



in puch situations it grows on hummocks the summits of which stand 

 above the water during the growing season. Unless the water level 

 is extremely variable or the ground is densely shaded, these hum- 

 mocks are usually covered with a cushion of live sphagnum moss. It 

 is a peculiarity of this moss that it absorbs water with great avidity; 

 indeed, sj^hagnum is one of the most absorbent substances known. If 

 one end of a nearly dry branch of sphagnum is brought into contact 

 with a little water, the whole branch becomes wet almost instantly. 

 The water rushes along with marvelous rapidity through the cells 

 of the plant and especialh' through the interstices between the minute 

 overlapping leaves. The white air spaces between the half dry leaves 

 flash out of existence one after the other like candle flames in a gust of 

 wind. The same ability to absorb water is characteristic of masses of 

 this plant. If the lower part of a cushion of sphagnum is in contact 

 Avith free water the fluid is conve^'ed from stem to branch and from 

 plant to plant in sufficient amount to render the whole mass as wet as 

 a sponge. When one squeezes a handful of such moss taken perhaps 

 a foot or more above the source of moisture the water runs out in 

 streams. A sample of live sphagnum with less moisture than usual 

 but still with enough to maintain itself in a growing condition was 

 found to contain 991 per cent of water, computed on the dry weight 

 of the sphagnum, while saturated live sphagnum carried 4,005 per 

 cent of water. On the basis of its dry weight, therefore, sphagnum 

 contains about ten times as much water as peat, which itself contains 

 about six times as much as ordinary loam and about thirty-five times 

 as much as sand. 



The innumerable extracapillary air spaces between the branches of 

 sphagnum plants and between the plants themselves furnish good 

 aeration, even when the individual branches are saturated with water. 

 AYhen the moisture is less the aeration is still better. The cushion of 

 sphagnum on a hummock tends to build itself up by the gradual 

 process of growth and decay to the maximum height to which it can 

 convey the large amount of water required for its growth, and an 

 increasing degree of aeration is found from the water line upward. 



If the sphagnum cushion on a blueberry hummock is examined the 

 whole mass will be found interlaced w^th the minute rootlets of the 

 ])lueberry, far above the level of the underlying soil. The conditions 

 of permanent moisture and thorough aeration found in these sphag- 

 num cushions seem to be almost ideal for the development of blueberry 

 roots. 



It must not be assumed that the vigorous growth of blueberry 

 roots in sphagnum is due to any high nutritive quality of the sphag- 

 num itself. Such a conclusion would be erroneous. Allien set out 

 in sphagnum and watered with tap water, blueberry plants remain 

 healthy and develop a very large root system, but the stems do not 

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