192 TRANSACTIONS AND PKOCEEDINGS OF THE [Sess. lvui. 



filled with water, one of the tubes being closely covered 

 with two or three folds of tinfoil, to exclude the light, 

 while the other was left clear. The carbonic anhydride, 

 evolved in each tube, was collected by absorption in the 

 potash bulbs and weighed. 



A few remarks on the respiration of germinating barley 

 will not be out of place at this point. 



During germination oxygen is absorbed and carbonic 

 anhydride excreted, the amount of the latter gas produced 

 being very slightly less in volume than that of the oxygen 

 absorbed, showing that a smaU quantity of oxygen is 

 retained by the corns, and is probably used up in other 

 changes. A certain quantity of water is also produced by 

 respiration ; and I have found that a fairly definite relation 

 exists between the weights of the carbonic anhydride and 

 the water. The numbers obtained indicate pretty plainly 

 the splitting up of a carbohydrate by oxidation. The 

 carbohydrate may belong to the cane sugar group repre- 

 sented by the formula C^o H22 On, the grape sugar group 

 C12 H24 O12. or the starch group, n (Cg Hjo O5). 



The oxidation by respiration of these carbohydrates may 

 be represented by the following equations, and it will be 

 observed that no more oxygen is required than is sufficient 

 to convert the carbon into carbonic anhydride : — 



1. Cane Sugar . Q^ H^, On + 24 = 12 CO^ + 11 OH, 



2. Glucose . C12 H., Oi, + 24 = 12 CO, + 12 OH, 



3. Starch . . C, Hj, O5 + 12 O = 6 CO, + 5 OH, 



The relation of the carbonic anhydride to the water will 

 be made simpler by taking the molecular weight of carbonic 

 anhydride 44, as a basis, then the ratios will be : — 



In one set of experiments on this point, the results of 

 which appeared in the paper referred to above, a ratio of 

 44 : 18"28 was obtained, while in a later series of experi- 

 ments, with a different barley, the ratio was 44 : 14"43. 

 The first result points to the splitting up of a glucose, and 

 the last to a splitting up of a starch. 



