THE SEED 77 



very soon reach c on one side and c f on the other. The 

 meaning of this experiment is obvious : the seeds in the 

 upper part of the vessel give off carbonic acid, which 

 as we know is greedily absorbed by caustic alkali, some 

 of which is contained in the beaker below them; conse- 

 quently, there is a decrease in the volume of air in the 

 whole apparatus, manifested by the rising of the column 

 of liquid in the left limb of the manometer. This experi- 

 ment proves that carbonic acid appears in exchange for 

 another gas, absorbed by the seeds ; because, if carbonic 

 acid were only added to the air enclosed in the apparatus, 

 one of two things would happen : either the volume of 

 air in the apparatus would increase, or else it would 

 remain unaltered (on the supposition that the whole of 

 the carbonic acid produced is absorbed by the alkali). 

 The decrease in volume depends on the absorption of 

 oxygen by the seeds ; in place of this oxygen an equal 

 volume of carbonic acid is generally given off, and this 

 is absorbed by the caustic alkali. Hence, this decrease 

 of volume serves both to measure the quantity of oxygen 

 inhaled and of carbonic acid exhaled. The column of 

 liquid rises so quickly that I shall have to open the 

 stop-cock (b) several times during the lecture in order 

 to keep the coloured liquid from running over into 

 the bell. This continual motion of the liquid in the 

 manometer demonstrates without further explanation 

 the invisible, inaudible, and yet fairly energetic breath- 

 ing of the seeds. 



The latest investigations prove that the formation of 

 diastase, a ferment already familiar to us, is apparently 

 closely connected with respiration. When seeds, already 

 swollen in water, were enclosed in a vessel filled with 

 hydrogen instead of air, they never developed, nor was 

 any diastase to be discovered in them ; whereas, when 

 seeds of the same kind were left in contact with air 

 they sent out shoots containing diastase. Thus it is 

 that we come to an understanding of one of the im- 



