August 11, 1916] 



SCIENCE 



211 



ture is due to the growth of the cortex on the 

 lower side of the stem. 



7. It is known that the geotropic " stimulus " 

 can travel around a corner, i. e., around an 

 incision through half the thickness of the stem, 

 which is to be expected if the " stimulus " con- 

 sists in the flow of a liquid. If such incisions 

 are made alternately across the upper and 

 lower half of each internode of a horizontally 

 suspended stem with only one leaf on the under 

 side, the stem will show geotropic curvature if 

 the leaf is in the apical node; but will show as 

 a rule no curvature if the leaf is in the basal 

 node; or a slight curvature in the neighbor- 

 hood of the basal node may occur after con- 

 siderable delay. 



8. All these experiments agree with the as- 

 sumption that each leaf sends a current of root- 

 forming substances towards the base of the 

 stem, and a current of shoot-forming sub- 

 stances towards the apical end of the stem; 

 that the root-forming substances have a ten- 

 dency to collect at the lower side of a hori- 

 zontally suspended stem, and that they are 

 associated or identical with the substances 

 causing the growth of the cortex on the 

 lower side of the stem to which the geotropic 

 curvature is due. 



9. This idea is further supported by experi- 

 ments with stems split into two longitudinally. 

 If such split stems are suspended horizontally 

 only those halves show geotropic curvatures 

 whose cortex is below. If the cortex is above 

 (and the cut surface of the stem below) almost 

 no geotropic curvature takes place, no matter 

 where the leaf is, for the simple reason that 

 such stems are lacking the cortex on the lower 

 surface. If the cortex is below and one leaf 

 left at the apical end, root-formation will take 

 place just as rapidly as in the intact stem and 

 geotropic curvature still more rapidly (since 

 the passive resistance of the upper half is re- 

 moved). If, however, the leaf is left at the 

 basal end, in about 50 per cent, of the cases no 

 geotropic curvature takes place, or if it takes 

 place it is confined to the region of the basal 

 node; and is considerably less than if the leaf 

 is left at the apical end. 



If the pieces have no leaf they will bend 

 more strongly than when a leaf is left at the 



basal end only, thus indicating a possible in- 

 hibiting influence of the basal leaf upon the 

 curvature in the more apical regions of the 

 split stem. 



10. All these facts suggest a close association 

 if not identity between the root-forming sub- 

 stances and the substances (or hormones?) 

 causing geotropic curvatures. Such a close 

 association or identity between organ-forming 

 and geotropic substances might also explain 

 why it is that in some cases geotropism can 

 restore the form in the same way as does re- 

 generation, as, e. g., in certain fir trees, where 

 one of the upmost horizontal branches will 

 begin to grow vertically when the apex is 

 cut off. Jacques Loeb 



The Rockefeller Institute for 

 Medical Eesearch, 

 New York 



THE AMERICAN CHEMICAL SOCIETY 



The 52d meeting of the American Chemical So- 

 ciety was held at the University of Illinois, Ur- 

 bana-Champaign, April 17 to 21, 1916. The meet- 

 ing was an unusually enthusiastic one, the total 

 registration being the largest to date, namely, 728. 

 A detailed description of the social and other 

 events of the meeting will be found on page 396 

 of the Journal of Industrial and Engineering 

 Chemistry for May, 1916. The general meeting 

 and meetings of the Divisions of the Society were 

 held in the lecture rooms of the chemistry building 

 of the University of Illinois. Some notable fea- 

 tures were presented in the "Special Program for 

 Home Economics" by the Division of Biological 

 Chemistry; in the "Symposium on the Activated 

 Sludge Method of Sewage Purification," by the 

 Division of Water, Sewage and Sanitation, and in 

 the ' ' Symposium on the Chemist in Pood Control, ' ' 

 by the Division of Agricultural and Pood Chem- 

 istry. 



The following general addresses were given: 

 The Composition of Corn as affected by Nineteen 



Generations of Seed Selection: L. H. Smith. 



(Lantern.) 

 The Manufacture of Chemical Apparatus in the 



United States: Arthur H. Thomas. 

 The War and the American Chemical Industry: 



Raymond F. Bacon. 

 On the Influence exerted by Electrolytes on the 



Equilibrium of Emulsions, Jellies and Living 



Cells: G. H. A. Clowes. (With demonstration.) 



(Lantern.) 



