CONSUMPTION OF CARBOHYDRATES DURING STARVATION. 71 



In order that the water-balance be maintained, the lower the water- 

 content the less can be the rate of water-loss at a constant rate of respiration ; 

 and, conversely, the lower the water-content the higher can be the respira- 

 tion at a constant rate of transpiration. The examples given in tables 35 

 and 36 will illustrate the point, 



TABLE 35. Loss in weight and rate of C0 2 emission of 

 Opuntia phGcacantha kept in dark at 28 C. 



The plants in table 35 had a relatively high initial water-content; they 

 were kept at 28 with a constant movement of air and, although the losses 

 were not uniform, they lost over 60 per cent of their total weight ; the water- 

 content was reduced by but 12 per cent. The plants in table 35 started with 

 a much lower water-content, which is reduced by only 9 per cent, with 

 decidedly lower total loss of weight and, relative to the total loss, a higher 

 rate of respiration. 



TABLE 36. Loss in weight and rate of CO Z emission of 

 Opuntia phceacantha kept in dark at 28 C. 



One example will suffice to illustrate the manner in which the two factors 

 of respiration and transpiration work together to maintain the water- 

 balance. In table 36 the first and second sets may be taken. In the initial 

 condition the plants emitted 0.25 mg. CO 2 per hour per gram dry material, 

 i. e., they were consuming at the rate of 0.00017 gram of sugar (CeH^Oe) 

 per hour per gram of dry material, or, calculated for the second set of plants, 

 0.0108 gram of sugar per hour. After 54 days there was produced CO 2 

 at the rate of 0.13 mg. per hour per gram of dry material, equal to 0.000089 

 gram of sugar per hour per gram dry material, or 0.0051 gram sugar per 

 hour for the entire set of plants. This would average 0.0079 gram of sugar 



