Roots and its Influence on the Ecesis of Plants in Swamps . 2 5 
and of others with the roots in moist soil. The results of these experiments 
indicate that transpiration is greater than absorption, and that the shedding 
of leaves is to be regarded as a compensation for reduced ability to absorb 
by a reduction of the transpiring surface. 
The Effect of Aeration on Submerged Roots. 
Arker ( 1 , p. 63) found that the rate of root growth of Lupinus albus and 
Helianthus animus could be increased by passing a current of air through 
water or soil. He also found that roots of plants in water readily take up 
oxygen in solution. Kraus ( 13 ) shows that the percentage of germination 
of seeds and the rate of growth of seedlings of land plants in the early 
stages of development can be greatly increased by supplying oxygen to the 
water in which the seeds or seedlings are submerged. Dachnowski ( 5 , 
p. 314) observed a stunting of roots in cultures of wheat, corn, bean, elm, 
and other plants in bog water. Aeration, he found, remedied the stunting 
effect. 
Hall, Brenchley, and Underwood ( 11 , p. 298), in an experimental study 
of soil solutions, found that a better root development and far better growth 
were obtained with silver sand and kaolin than with fine sand, silt, or in 
water culture. It was suspected that differences in aeration of the roots might 
be the disturbing factor. The correctness of this supposition was established 
by growing barley in culture solutions aerated once a day and aerated con- 
tinuously. The latter gave much the better root development, and also the 
better growth of leaves and stems. 
Hole ( 12 ), as a result of the study of the reproduction of Shorea 
robusta , came to the conclusion that the failure of reproduction was due 
to poor aeration, and states (p. 80) that when proper aeration was provided 
the injurious effects were quickly dissipated. 
Experiments of the writer also show that when aeration is provided 
the development of roots under submergence is not much, if at all, retarded 
as compared with the growth of roots in moist soil. No essential difference 
was to be observed in the behaviour of plants with the roots submerged in 
swamp water as compared with other plants of the same kind with the 
roots in tap-water. In either case symptoms of distress were manifested 
in equal degree in the same period of time, and in either case the plants 
recovered with equal promptness when air was supplied. In the experiment 
described on p. 2i 3 only a slight difference in the size and vigour of the 
plants watered with nutrient solution as compared with those watered with 
swamp water was observed. The plants in both cases were under the same 
conditions of aeration, so that differences of size or vigour cannot be ascribed 
to that cause. The slightly poorer growth noted in the plants watered with 
swamp water was probably due to a lack of potash or nitrates or both. 
