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INFLUENCE OF GRAVITY ON ARRANGEMENT OF ORGANS 



appear or be greatly diminished, since the influence of the water 

 furnished from the outside might tend to make the influence of the 

 slight quantity of sap collected on the lower side through the influence 

 of gravity a negligible factor. 



When we suspend pieces of stem of Bryophyllum horizontally under 

 water (instead of in air) roots no longer develop on the lower side 

 only but on the upper side as well (Figs. 2 and 3). The sap will in 

 this case collect also in somewhat greater abundance on the lower 

 side of the stem, but this will cause no retardation of growth on the 



Fig. 2. Stems suspended horizontally under water. Roots form no longer 

 exclusively on the lower side of the stems as they would have done had the stems 

 been suspended in air, but on both the upper and lower side of the stem. The 

 stems were originally straight and the curvature is due to geotropism; i.e., greater 

 growth on the lower side. 



upper side on account of the abundance of water on the upper side 

 of the stem. This is also true for leaves. When we suspend leaves 

 vertically and sidewise under water the roots and shoots will develop 

 equally fast on the upper and lower sides of the leaf and the influence 

 of gravity will disappear (Fig. 1, lower row). In both cases it is 

 necessary to suspend the organs near the surface of the water so that 

 their oxygen supply will not suffer too much. 



