56 



Journal of Applied Microscopy. 



An Osmometer and Root-Pressure 

 Apparatus. 



D. T. MacDougal. 

 A good osmometer is essential to the 

 equipment of every physiological labora- 

 tory or lecture room, and the demonstra- 

 tive value of such apparatus is greatly 

 increased when its action can be com- 

 pared directly with that of the organ- 

 ism. The osmometer described below 

 has been devised from this point of 



M 



EXPLANATION OF FIGURE. 

 A, glass vessel containing distilled water. 

 B, parchment cylinder, to contain sugar so- 

 lution. C, stopper. D, base of connecting 

 tube to which a separatory funnel is fused. 

 E, capillary extension tube. G, joint made 

 with rubber tubing wired. M, manometer 

 tube. 



The diffusion membrane consists of a 

 section of parchment tubing twenty-five 

 centimeters in length and five centi- 

 meters in diameter when inflated. The 

 tubing is soaked in water for an hour, 

 then a small portion at one end is pleated 

 compactly, doubled back and tied firmly 

 with cord. A perforated cork or rubber 

 stopper is fitted to the other end and 

 secured by a wrapping of cord. The re- 

 maining essential part of the apparatus 

 consists of a separatory funnel fused at 

 right angles to the short horizontal of a 

 T tube. The lower vertical arm of the 



tube is inserted in the perforation of the 

 stopper. The upper vertical arm is 

 joined to a capillary tube of the same 

 external diameter by means of rubber 

 tubing wired. This extension tube may 

 be of any desired length. The writer 

 uses one two meters long. Previously to 

 the addition of the extension tube, the 

 parchment cylinder is filled with the 

 sugar solution or liquid to be tested, and 

 surrounded by a cylinder filled with dis- 

 tilled water. 



The great surface of the parchment 

 forces the fluid upward so rapidly — about 

 one centimeter per minute — that its 

 movement in the capillary tube may be 

 followed with the eye across a lecture 

 room. A few drops of analine dye added 

 to the upper vertical arm of the T tube 

 before adding the extension tube will 

 make the column more easily visible. 



The form of the parchment cylinder 

 resembles that of a root-hair, and if the 

 membrane is impregnated with copper 

 salts in the usual manner, it will repre- 

 sent quite fairly the physical conditions 

 of absorption by roots. 



The parchment cylinder may be 

 quickly detached, and the stump of a 

 bleeding plant put in its place, giving a 

 comparison with root-pressures. A 

 manometer consisting of a U tube with 

 a bulb in the short arm may be used 

 instead of the vertical extension tube, 

 and the osmotic and root-pressures may 

 be read in terms of the mercury column. 



University of Minnesota. 



A Convenient Paraffin Imbedding 

 Dish. 



The following simple method of mak- 

 ing a paraflin imbedding dish I have 

 found very convenient. A Stender dish 

 of the desired diameter, depending on the 

 amount of material to be imbedded, is 

 inverted and a piece of firm paper is 

 wound tightly about it so that the edge 

 of the paper projects one centimeter or 

 more above the glass bottom. The free 

 ends of the paper are allowed to over- 

 lap and are held together by a piece of 

 gummed paper placed on the outside. 

 The glass bottom of the Stender dish 

 and the paper constitute the imbedding 

 dish. The glass bottom of the dish is 

 coated with glycerine, so that the par- 

 affin block can readily be removed. 

 When the paraffin is sufficiently cooled, 

 invert the dish and allow water to run 

 into the Stender dish, thereby cooling 

 quickly the paraffin on the side next 

 the glass. The paper can then be torn 

 away. By its use a person can dispense 

 with the ordinary " L's " and other 

 appliances. E. Mead Wilcox. 



Lab. of Veg. Physiology, Harvard Uni- 

 versity, Cambridge, Mass., Feb. 8, 1898. 



