March 7, 1913] 



SCIENCE 



379 



these increase until the hypoeotyl is 3-5 cm. long. 

 At this time the fats decrease and sugar appears. 



The after-ripening period can be shortened 

 greatly by treating the embryos with dilute solu- 

 tions of HCl, butyric and acetic acids. The water- 

 holding power, the acidity and the activity of 

 peroxidase increase much more rapidly than in the 

 untreated embryos. 



The Vse of Celloidin Memhranes for Demonstra- 

 tion of Osmosis: G. M. Smith, University of 



Wisconsin. 



The membranes were prepared by pouring a 

 10 per cent, solution of celloidin on a dish of 

 clean mercury and, after allowing the celloidin to 

 dry sufficiently to be lifted, it was placed over the 

 end of a thistle tube, tied down and allowed to 

 harden. Two membranes were made, one over the 

 other; the double membranes proving themselves 

 ten times as strong as the single ones. The tensile 

 strength of the membrane was found by setting 

 up the osmometer and pouring in mercury and 

 noting the height of the column, when the rupture 

 of the membrane occurred. The double mem- 

 branes stand over three atmospheres pressure with- 

 out breaking. 



The membranes were rendered semipermeable by 

 putting a M/20 potassium ferrocyanide solution 

 inside of the osmometer and immersing the appa- 

 ratus in a M/20 copper sulphate solution. A good 

 membrane is formed within the celloidin in three 

 days. When a celloidin membrane separates water 

 and a 3M cane sugar solution the liquid in the 

 osmometer will rise about seven feet in three 

 days and then sink ; but when the celloidin mem- 

 brane contains a copper ferrocyanide precipitate 

 the liquid will rise about twenty-five feet in ten 

 days and then slowly sink. 

 Studies of Osmotic Pressure: M. A. Brannon, 



"University of Chicago. 



This report is based upon studies made in the 

 plant physiological laboratories at the University 

 of Chicago. The work extended over a period of 

 ten months. The measurements of osmotic pres- 

 sure were made by eryoscopie methods, the Beck- 

 mann apparatus being employed to determine the 

 freezing points of the solutions used. 



Three different kinds of potatoes were chosen. 

 They were placed in controlled conditions so that 

 only one limiting factor, heat, was involved in the 

 experiments. One collection of potatoes was 

 placed in an icebox where a temperature of 2° C. 

 was maintained and one collection was kept at a 

 temperature of 25° 0. 



At the beginning of the experiments the os- 

 motic pressure of the different potatoes was about 

 7 atmospheres. After ten months the icebox 

 potatoes had developed a maximum osmotic pres- 

 sure of 13 atmospheres. The lower temperature 

 favored metabolic activities resulting in the lib- 

 eration of an acid, a catalyte and the fermenta- 

 tion of foods, stored in the form of starch and 

 hemicellulose. The change from colloids to crys- 

 stalloids was accompanied by the rise in osmotic 

 pressure noted. 



The fermentation of the hemicellulose was indi- 



' cated microscopically by the great reduction in 



the thickness in the cell walls of the potato tissue 



affected, and also by the great increase in the 



brittleness of the potato tissues involved. 



These studies are suggestive of the changes 

 taking place in the after ripening of seeds, tubers 

 and bulbs, and has a definite relation to several 

 economic and scientific problems. 



Protoplasmic Contractions Uesemhling Plasmolysis 



which are caused hy Pure Vi'itiUed Water: W. 



J. V. OsTEEHOUT, Harvard University. 



True plasmolysis can be produced only by solu- 

 tions which are hypertonic, but appearances almost 

 or quite undistinguishable from it may be brought 

 about by hypotonic solutions. Some light is 

 throvm on the nature of this result by a study of 

 certain cases in which it is caused by pure distilled 

 water. Material for such study is afforded by 

 marine plants. 



The root tips of the eel grass {Zoster a marina) 

 are well adapted to this purpose. The root tips 

 were carefully removed from the sand in which 

 they were growing and immediately placed in sea 

 water. 



The application of distilled water causes a con- 

 traction of the protoplasm which often closely 

 resembles the true plasmolysis produced by hyper- 

 tonic sea water (which has been concentrated by 

 evaporation) or by hypertonic sugar solutions. 

 The mode and the degree of contraction vary 

 somewhat, but in general the variations ia true 

 plasmolysis are of the same sort, as in what may 

 be conveniently called the false plasmolysis. We 

 may use the term false plasmolysis to designate 

 not only the contraction produced by distilled 

 water, but also that which is caused by certain 

 hypotonic solutions. 



The Effect of Anesthetics on Permeability: W. J. 

 V. OsTBRHOUT, Harvard University. 

 Experiments were performed to test the elec- 



