196 WATER CTTLTTTRE, PHOTOSYNTHESIS, RESPIRATION. 



well for experiments with small seeds. Along with the 

 seeds insert in each case a small bottle containing a piece 

 of potash stick, covering the mouth of this bottle with 

 wire netting ; insert the thermometer and pack the space 

 between it and the neck of the vessel with cotton- wool. 



(2) In the absence of a better form of non-conducting 

 chamber, we may either (a) line a funnel with filter-paper, 

 fill it with the seeds, and support it with the tube dipping 

 in a bottle of potash, insert a thermometer, and cover the 

 whole with a bell- jar ; or (6) place in a tumbler a flat dish 

 of potash, cover this with wire gauze, and insert the seeds 

 and a thermometer ; or (c) place the seeds in a small 

 flower-pot, set this in a larger pot with wool or other 

 packing between the two pots, cover the mouths of the pots 

 with wire gauze, invert the apparatus over a saucer with 

 potash stick, and insert a thermometer through the holes 

 in the two pots ; or (d) put potash stick in a beaker, then 

 wire gauze, then seeds, then a cork bored for the ther- 

 mometer, and place the beaker inside a larger beaker lined 

 with wool. 



In each case it is advisable to set two controls in one 

 place seeds boiled and treated with antiseptic (formalin or 

 corrosive sublimate), in the other wet sawdust instead of 

 the seeds. Opening buds, flowers, and flower-heads should 

 also be used ; a remarkably large rise in temperature is 

 observed in the case of the opening inflorescence of Arum 

 and other Aroids. 



259. "Intramolecular" Respiration. In some of the pre- 

 ceding experiments it was noticed that the amount of carbon 

 dioxide set free is much greater than that of the oxygen absorbed 

 e.g. in germinating Peas. This suggests that in such cases there 

 might be a release of carbon dioxide even in the absence of a supply 

 of free oxygen, and it is easy to test this by placing such seeds in 

 " an anaerobic culture vessel" i.e. a vessel from which oxygen is 

 excluded, though other conditions are favourable for respiration. 

 Such a vessel may be either (1) a short tube filled with mercury and 

 inverted over mercury, the seeds being passed up to the closed end 

 of the tube ; (2) a similar tube over 76 cm. long and therefore with 

 a Torricellian vacuum, in which the seeds are placed ; (3) a seed- 

 containing chamber filled with pure hydrogen, which is afterwards 

 analysed for carbon dioxide. 



