248 PLANT PHYSIOLOGY 



inner cone) of a Bunsen flame, and slowly revolved, small tubing will seal 

 itself together perfectly. Or, if the precise shape does not matter, it may 

 be held in a flame until it softens, when, if drawn apart, it will seal itself with 

 a conical tip, and this is the best method with tubing above 6 mm. diameter. 

 An open capillary point may be sealed by a very tiny flame, even of a match. 



Smoothing cut ends. Hold the rough parts in the Bunsen flame until they 

 fuse smooth. Or grind them upon an emery-wheel (page 48). Small 

 tubing may be thrust at once into the flame, but large tubing must be brought 

 into it cautiously. The rough ends of fine capillary tubing (which may be 

 cut across with scissors) may be smoothed by careful rubbing on an oilstone, 

 or on a piece of ground glass, or by cautious fusing. 



GROUND STOPPERS, when stuck, may be loosened thus: If the top 

 of the stopper is flat, place this in the hinge-crack of a door partly closed upon 

 it, turn the bottle gently, when the stopper will probably loosen. Or, hold- 

 ing the bottle suspended by the stopper a half inch above the table, tap the 

 stopper with a wooden hammer-handle or equivalent, when the bottle will 

 usually drop from the stopper. Or twist a cotton rag into a spiral roll sev- 

 eral inches long, and dip it into boiling water, excepting the ends, which are 

 held; twist it quickly around the neck of the bottle, when the heat swells 

 the neck and usually loosens the stopper. Or revolve the neck of the bottle 

 quickly in the Bunsen flame, when the swelling of the neck will loosen the stop- 

 per. It is also said that the friction of a silk handkerchief rapidly drawn 

 across and around the neck of the bottle will warm and swell it enough to 

 loosen the stopper. 



HEAT. Separation from light may be effected by interposition of an 

 alum bath; but for most purposes running water from a tap carried through 

 a flat-sided chamber, e.g., a gas-chamber (page 72), is more convenient, 

 especially where the microscope is concerned. 



HOODS. If used for darkening plants, they should be black inside, 

 but white outside in order to prevent excessive heating. It is well to have 

 a supply always ready, made of black sateen and white cambric, of a size 

 to fit the standard bell jars. A paper, black on one side and white on the 

 other, is obtainable from supply companies. Gray felt paper makes a good 

 compromise material. 



HYDROSTATS. Water-levels may be kept constant in various ways. 

 The Mariotte device consists of a water-filled inverted vessel with its outlet 

 just above the level to be maintained; as the water-level falls air is admitted 

 to the vessel, thus allowing water to escape and raise the level. An inverted 

 bottle, with a grooved cork projecting just so far from the neck as the desired 

 depth of the water, serves very well. Or the bottle may be placed at a 

 distance, with a glass tube extending to the desired water-surface. Different 

 arrangements are figured in the first edition of this book, pages 108, 100. 



For keeping a water-supply constant in soil, there is an arrangement by 

 Krutitzky (see Buhgerstein, " Die Transpiration," 22), while a recent 

 and efficient arrangement is Livingston's (see page 176 of this book). 



HYGROSCOPICITY. For overcoming this in threads see page 204 



JOINTS. See Connections. 



