24 6 PLANT PHYSIOLOGY 



the surface of the stem is channelled or otherwise irregular, some firm wax 

 (see below) should be used between stem and rubber. 



Stems to bored glass plates and necks of bottles. Use a bored-and-split 

 soft-rubber stopper, with firm wax (described below). O, seal with mer- 

 cury by a method given in MACDOUGAL, 229. Or use gelatin by DEVAUX'S 

 method (DARWIN and ACTON, 108). 



CORKS. Air-tightness is secured by soaking them in melted hard 

 paraffin (in a water-bath), or, less efficiently, by smearing with vaseline. 



Boring for tubes, etc., is effected by standard cork-borers, helped by 

 round files. 



Improvement is made in every way through softening them by a cork- 

 presser, of which the rotary form is best. 



Insertion into nearly full bottles may be effected by interposing between 

 cork and glass a thread or a wire (finally withdrawn) along which the air 

 may escape. 



DRAWINGS. See Blue-prints. 



EVAPORATION. Prevention is possible thus: If a free water-surface, 

 cover with a film of oil, preferably machine-oil. If a moist surface, work 

 over it a thin coating of modelling-wax. For other methods see page 173. 



GERMINATING SEEDS. See page 210. 



GLASS BOTTLES. Cleaning from tenacious sediment is effected by 

 vigorous shaking with water and small shot, the latter kept stored in a bottle 

 for the purpose. 



Boring holes of any desired size may be accomplished by use of the end 

 of a round file rotated with a carpenter's brace and kept wet with turpen- 

 tine and camphor (12 weights of turpentine to i of camphor, freshly prepared). 

 Or emery flour and camphor are said to be excellent, and better yet is den- 

 tists' carborundum. Instead of the file a drill may be used, or even, it is 

 said, a brass cork -borer held in position in a hole bored in a wooden block 

 cemented to the glass. 



Cutting across. See under Glass Tubing, Cutting. 



Labelling. See Labels. 



GLASS FILAMENTS. May best be made from Glass Tubing, 

 Capillary, which see. 



GLASS TUBING. On manipulation there is a very useful little hand- 

 book, "The Methods of Glass-blowing," by W. A. SHENSTONE (London, 

 Longmans, Green, Si Co., 1902). 



Bending. The smoothest bends can be made by heating the tube, which 

 is kept revolving, in a luminous flame of the fish-tail form (or in the Bunsen 

 wing-top), and the bend is better if the softened glass is allowed to settle by 

 its own weight. The tube is held lengthwise in the flame for very gradual 

 bends, and obliquely for shorter turns. For special curves, etc., the hot glass 

 may be moulded by a cold iron. 



Capillary. Hold the smallest available glass tubing in the Bunsen flame, 

 revolving it until soft, and then pull apart the two ends. The fineness of the 

 tubing can be controlled by the degree of heating and rapidity of the drawing- 

 out. To keep the capillaries straight, pull up and down, not horizontally. 



