336 MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 



determine together groups of sugars of the same general physio- 

 logical significance. It has been found preferable for the present to 

 make a large number of analyses with as great accuracy as possible, 

 rather than attempt to isolate and determine each of the sugars in 

 a few cases, especially as individual cases show considerable varia- 

 tion. For the present purpose a discussion of the methods of 

 analysis^^ employed does not seem essential. 



The following experiment will illustrate the efifect of water on 

 the carbohydrate balance of Optintia discata. A number of joints 

 of the same age were taken from one plant and divided into three 

 lots each of six joints. The first (i) was analyzed immediately, 

 the second (2) was suspended in battery jars without water, and 

 the third (3) was placed in the same manner in battery jars so that 

 the base of the joints were immersed as in a water-culture. (2) 

 and (3) were kept in a dark constant temperature' room at 28° for 

 thirty days, when they were analyzed. The joints in water had 

 developed roots 5 to 10 cm. in length. 



Immediate (i). 



Fresh. Dry. 



Dry (2). 



Fresh. 



Dry. 



Water (3). 



Fresh. Dry 



Water 



Total sugars 



Total polysaccharides 



Hexose-polysaccharides . . . 

 Disaccharides and hexoses. 



Disaccharides 



Hexoses 



Pentosan 



50.34 

 4-30 

 3-50 

 1.6s 



O.IO 



0.04 

 0.06 



1.74 



20.49 



17.80 



8.40 



0.49 



0.20 

 0.29 



8.86 



77.20 

 4.29 

 3.60 

 1.81 

 0.13 

 0.07 

 0.06 

 1.78 



18.01 

 8.83 

 0.56 

 0.30 

 0.26 

 9.18 



52.30 

 3-6o 

 2.80 



1. 25 



0.14 

 0.06 

 0.08 

 1.25 



18.58 

 17-54 

 7-85 

 0.83 

 0.38 

 0.45 

 7-85 



The joints without water (2) lost 3.14 per cent, in water con- 

 tent, while those in water (3) gained 1.96 per cent. In total poly- 

 saccharides and hexose-polysaccharides (3) is considerably lower 

 than (2), while in hexoses (3) shows a gain over (i) and (2). 



The difi^erence in the carbohydrate balance between plants grow- 

 ing in the desert and in Carmel, California, is illustrated in the 

 following analyses of Opttnth sp. during September. The values 

 are per cent, of fresh weight : 



1'^ Full particulars thereof will appear in a later publication on the " Car- 

 bohydrate Economy of Cacti." 



