RECENT ADVANCES IN SCIENCE 455 



bedded character, and by having a composition like that of a 

 siliceous mud, similar to present-day loess. 



Economic Geology. — As the greatest corundum deposits of 

 the world occur in Ontario it is appropriate that an exhaustive 

 treatment of the occurrence, origin, distribution, and economic 

 uses of this mineral should appear in a Memoir (No. 57, by 

 A. E. Barlow) of the Canadian Geological Survey. The corun- 

 dum occurs as an original pyrogenetic constituent of certain 

 nepheline-syenites and anorthosites belonging to the Archaean 

 of the Canadian Shield. 



BOTANY. By F. Cavers, D.Sc, A.R.C.Sc. 



Plant Physiology . — A large amount of attention has recently 

 been given by plant physiologists to antagonistic ion action and 

 some related phenomena, and the results already obtained 

 mark a great advance in the knowledge of the complex relations 

 involved in the exchange of substances between the exterior 

 and the interior of the cell. The modern conception of an- 

 tagonism — that is, the mutual hindrance between salts, or more 

 properly between ions, in their absorption in solution by cells — 

 dates from Loeb's discovery in 1901 that certain animal eggs 

 cannot form an embryo if placed immediately after fertilisation 

 into a solution of pure NaCl of the same concentration as that 

 of this salt in sea-water, but that the toxicity is reduced if a 

 small quantity of the salt of a bivalent metal is added to the 

 NaCl solution. Further work on both plants and animals has 

 shown that antagonism is a phenomenon of widespread if not of 

 universal occurrence in organic life, that it is with very few 

 exceptions limited to kations, and that the effect is greatest 

 between ions of different valency. Following up their useful 

 resume of the literature, published last year (New Phyt. 13), 

 Stiles and Jorgensen have now described (Ann. Bot. 29) the 

 results of experiments on the exosmosis of electrolytes as a 

 criterion of antagonism, in which they attacked the problem of 

 the relations between plant tissue and a solution surrounding 

 it b} r examining the changes in electrical conductivity of the 

 latter. They conclude that within limits the rate of exosmosis 

 is a measure of toxicity, and that a decrease they have observed 

 in this rate when certain ions are added to solutions containing 

 poisonous ions may be due to the same cause that produces what 

 other investigators have called antagonism. That is, the 



