38 EXPEETMENTS IN BLUEBERRY CULTURE, 



remaining in the soil after this treatment is known as the moisture 

 equivalent of that soil. A test of kalmia peat made by Dr. Lyman 

 J. Briggs, of the Bureau of Plant Industry, the originator of this 

 method of measurement, showed a moisture equivalent of 142 per 

 cent, as compared with about 30 per cent for clay, 18 per cent for 

 loam, and 2 to 4 per cent for sand. 



From Avhat has been said it is evident that fibrous kalmia peat 

 has physical characteristics that allow the soil to be amply aerated, 

 while at the same time holding abundant moisture for the supporting 

 of plant growth. 



In this connection reference may be made to the influence of earth- 

 worms on potted blueberry plants. Late in the winter of 1908-9 

 it was noted that among the blueberry seedlings of 190T, which had 

 been brought into the greenhouse, were several in which the growth 

 was feeble, although others of the same lot were growing vigorously. 

 It was noted also that the soil in the pots in which the feeble plants 

 were growing contained earthworms, as evidenced by the excre- 

 ment or casts deposited b}^ them on the surface. The worms 

 themselves were easily found by knocking the earth ball out of the 

 pot, and the soil was seen to have been thoroughly worked over by 

 the worms. 



It was supposed at first that the soil (a mixture of peat 8, sand 1, 

 loam 1) in the process of digestion to which it had been subjected 

 in passing through the alimentary canal of the earthworms might 

 have become alkaline and for this reason injurious to the blueberry 

 plants. When tested with phenolphthalein, however, the soil in the 

 pots containing earthworms and feeble plants was found to be of the 

 same acidity as that in the pots containing no earthworms and with 

 vigorously growing plants. Furthermore the fresh casts themselves 

 were of a similar degree of acidity. 



The texture of the soil, however, in the pots containing worms was 

 very different from that in the others. It was plastic, very fine 

 grained, almost clayey, the organic portion having been very finely 

 ground evidently in passing through the gizzard and other digestive 

 apparatus of the eartliAvorms. The aeration of the soil in this condi- 

 tion must have been far poorer than in the coarser soil containing a 

 large amount of leaf fragments not worked over by worms, and it 

 may be that the difference in growth of the blueberry plants was due 

 to the difference in aeration. It is not by any means certain, however, 

 that the plants in the pots containing earthworms may not have been 

 injured directly through the eating of their rootlets by the worms. 



(12) Aeration conditions satisfactory for the swamp blueberry are found 

 in masses of live, moist, but not submerged sphagnum. 



In some swamps the water level remains permanently above the 

 general surface of the ground. AMien the swamp blueberry occurs 



193 



