238 



RESPIRATION 



With these the mercury rises in the tube, for the volume of oxygen absorbed 

 by them is greater than that of the carbon dioxide emitted. 



Ex. 140. — Show that heat is developed during respiration of germinating 

 seeds. 



Soak some barley grains or peas 

 in water for a fewr hours and then 

 allow them to begin germinating on 

 damp blotting-paper. Place them in a 

 large glass funnel {B), supported in a 

 beaker or glass cylinder (C) containing 

 a small quantity of a strong solution of 

 potash (Z>) as in Fig. 90 ; dip into 

 the seeds the bulb of a thermometer (A) 

 reading to half a degree. Cover the 

 whole loosely with a cardboard or 

 wooden box (£), leaving a hole in the 

 top for the thermometer tube. 



For comparison, fit up a similar 

 apparatus by the side of the first with 



balls of blotting-paper soaked in water '/-^'^^ ''"-«' -'---J ^ 

 in the funnel instead of seeds ; compare 

 the readings of the two thermometers on three succeeding days. 



Anaerobic or Intramolecular respiration. — When living plants 

 or parts of plants are placed in an atmosphere devoid of free 

 oxygen, they continue to give off carbon dioxide gas for a longer or 

 shorter time before death occurs. This production and evolution 

 of carbon dioxide by living organisms in the absence of free 

 oxygen is termed anaerobic or intramolecular respiration. 



The length of time which plants will live under these circum- 

 stances depends upon the kind of plant and the vigour of its 

 growth : actively-growing maize seedlings live and continue to 

 give off carbon dioxide in the absence of oxygen, for twelve 

 or fourteen hours at ordinary temperatures, while ripe fruits, 

 such as pears and apples, live for several months under similar 

 conditions. 



In the majority of cases the amount of carbon dioxide thus 

 produced is considerably smaller than that which is given off 

 by the same plants when exposed to the air ; for a short time, 



