SEEDS AND SEEDLINGS. 



31 



56. Respiration of Germinating Seeds. These experi- 

 ments show that germinating seeds absorb oxygen and give out 

 carbon dioxide, so that a germinating seed changes the air 

 around it in the same way that an animal does by its breath- 

 ing. Since the same change is produced by burning in air a 

 candle (which contains carbon) or a piece of charcoal (which 

 is practically pure carbon), we see that the respiration or 

 breathing of a germinating seed, or of an animal, is simply a 

 process of oxidation, a slow burning of carbon. Hence the 

 seed must contain carbon in some form ; we shall return to 

 this point later. Meanwhile, here are some further experi- 

 ments on the respiration of germinating seeds. 



* (a) Get a wide-mouthed jar with a tightly fitting cork ; bend a glass 

 tube twice at right angles, so that the two parallel legs will be of about 

 equal length, and through a hole in the cork push one of the legs until 



Fig. 18. 



Fig. 19. 



it nearly reaches the bottom of the jar (when corked). Fill a small 

 muslin bag with soaked Peas, mixed with bits of soaked Sphagnum or 

 clippings of wet sponge, and hang the bag to the lower side of the 

 cork by means of a bent pin. Put a bit of sponge soaked in caustic 

 potash solution 1 in a small wide-necked bottle or an egg-cup and lower 

 it into the jar (Fig. 18). Smear the top of the cork and the rim of the 

 jar with plasticine. Put the outside tube in a tumbler or open bottle 



1 This solution rapidly absorbs any carbon dioxide in its neighbour- 

 hood, but the carbonate of potash formed is soluble. 



