DEPARTMENT OF BOTANICAL RESEARCH. 



81 



proportion of water being found after six years of desiccation in the 

 case of one plant as was present in the beginning, in spite of a loss 

 of nearly 30 per cent of its original weight by water depletion.^ These 

 results were very striking, and it seemed that it would be of unusual 

 interest to combine these effects in one plant, thereby obtaining new 

 light on the course of katabolism in the various types of carbohydrate 

 and on the time element involved. 



Accordingly, an echinocactus, which had been loaded with carbo- 

 hydrate by desiccation in the open, after 8 months was placed in a 

 ventilated dark chamber where photosynthesis was no longer possible 

 and katabolism would go on mthout extensive repair. No. 23 of the 

 series was chosen for this puipose because in treatment, appearance, 

 and amount of water-loss it was comparable to No. 22, a plant desic- 

 cated in the open, the analysis of which has been recorded in the 

 following table. 



The principal findings embodied in the following table may be 

 briefly set forth as follows: The rate of water-loss tends to become 



Resvlts of analyses of Echinocactus. 



Analyses made. 



No. 23. 

 Desiccated in full 

 sunlight 8 months 

 10 days and in 



darkness 22 



months 17 days. 



Total water-loss 



57.2 per cent. 



No. 7. 



Desiccated in diffuse 



light 6 years 1 



month. 



Total water-loss 



29.3 per cent. 



No. 22. 



Desiccated in full 



sunlight 5 months 



6 days. 



Total water-loss 



40 per cent. 



No. 34. 

 Normal, not 

 desiccated. 



Dry weight per cent of 

 total weight 



Sap (density water = 1 .00) 



Sap acidity, N/10 



Total hj-drolj'zable car- 

 bohydrate, per cent of 

 total solids 



Total reducing sugars, 

 per cent of total sap- 

 weight 



Total non-reducing su- 

 gars, per cent of total 

 sap-weight 



ab 



20.2 

 1.018 

 0.600 



31.5 



O.OS 



trace 



a 



17.1 

 1.035 

 0.400 



28.2 



trace 



trace 



9.5 



1.010 



1.144 



22.3 



0.09 



0.11 



8.0 



1.018 



0.104 



24.2 



0.06 



0.10 



5.8 



1.013 



0.148 



11.1 



0.04 



0.06 



a 



14.3 

 1.016 

 0.244 



44.3 



0.15 



1.28 



13.3 

 1.027 

 0.208 



44.2 



0.13 



1.48 



11.3 

 1.034 

 0.156 



43.4 



0.10 



2.67 



5.8 



1.013 



0.172 



32.3 



0.53 



0.14 



4.2 



1.011 



0.156 



35.7 



0.42 



0.03 



3.6 



1.011 



0.128 



29.6 



0.10 



0.05 



constant in darkness ; the acidity increases in darkness ; soluble sugars 

 are broken up, while but little change has taken place in the insoluble 

 polysaccharids. The total hydrolyzable carbohydrate content of No. 

 23, after its prolonged stay in darkness, is hardly less than that of the 

 normal, No. 34, and is lower than that recorded for No. 22. The high 

 figure for total hydi'olyzable ca,rbohydrates in No. 22 is due in a large 

 measure to the high concentration in the pulp of soluble non-reducing 



^MacDougal, Long and Brown, The End Results of Desiccation and Respiration, Physi- 

 O'Ogical Researches Xo. 6, Aug. 1915. 



