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XXXV. 



A PRBLIMINAEY ACCOUNT OF A NEW OEDANOMETER FOR 

 MEASURING THE EXPANSIVE FORCE OF SINGLE 

 SEEDS, OR SIMILAR SMALL BODIES, WHEN WETTED. 



By J. BATLET BUTLER, M.A., M.B., 

 Professor of Botany, University College, Dublin ; 



AND 



JOHN M. SHERIDAN, B.A., M.Sc, 

 Assistant in the Biological Department of University College, Galway. 



[Read December 15, 1914. Published March 29, 1915.] 



The question of the absorption of water by seeds has hitherto been studied 

 mainly by investigation into the quantity absorbed, and the volume changes 

 which the seed undergoes. 



The fact that seeds, and other organic bodies, during the swelling which 

 accompanies this absorption of water, can exert a considerable pressure has 

 long been recognized. This phenomenon has been put to practical use in the 

 splitting of rocks by wooden wedges wetted with water ; by the disarticu- 

 lation of skulls through tlie swelling power of peas ; and by the action of 

 Laminaria tents in dilating the Os uteri. 



It appeared to us that it might prove to be of interest to attempt to 

 measure the maximum pressures which are generated by swelling organic 

 bodies ; and later, if possible, to determine the influence of altered conditions 

 such as temperature, saline solution, or absence of life in seeds on tliese 

 pressures. 



In the following paper we give a brief account of an instrument, which 

 we may term " Oedanometer " {olSaveiv = to cause to swell),' which we have 

 designed to record the pressures generated by single large seeds or similar 

 bodies. 



Only a few records are given ; further records and a discussion of the 

 results will form the subject of a subsequent paper. 



' Eeinke (13) uses the term " Odometer " for his apparatus, which measures primarily the volume 

 changes of swelling bodies rather than the force with which the body swells. It appeared lo us that 

 it would avoid confusion if we used the term " Oedanometer" for this apparatus, which measures the 

 force rather than the volume of swelling. 



