CH. Il] ASSIMILATION OF SUGAR. 33 



or Callitriche, are placed in vessels of 500 c.c. capacity, 

 containing spring water, to one set of which (A), 3 % cane- 

 sugar has been added, to (B), 5 % glycerine, while to (C) 

 nothing has been added. It is of importance that speci- 

 mens similar in size and in general vigour shall be selected, 

 and that the specimens should be small in comparison 

 with the volume of water in the beaker. Leave the vessels 

 in the dark room for 8 or 10 days 1 , when the plants in 

 (A), (B) and (C) are to be compared as to condition, 

 growth, and especially as to the contained starch. The 

 control specimens will be starchless, and dead or nearly so, 

 while the experimental plants will be obviously better 

 nourished and will contain more or less starch. The 

 glycerine cultures do not as a rule succeed so well as 

 those in cane-sugar. The chief difficulty experienced is 

 the growth of moulds in the solution. Something may be 

 done by washing the vessels with -Jp.c. corrosive sublimate 

 and then in boiled distilled water ; the culture fluids 

 should be boiled and allowed to cool in vessels closed with 

 cotton-wool plugs. [See Chap, iii.] 



Chlorophyll is not necessary for this form of assimila- 

 tion, colourless parts of plants form starch vigorously. 

 The white flowers of PJdox paniculata are especially 

 useful for this experiment. They are simply floated in 

 the above-described solutions of sugar or glycerine, control 

 specimens being placed in water. In a few days they 

 become rich in starch, while the control flowers are 

 starchless. The employment of colourless objects, such 

 as white flowers, is especially convenient, since the use of 



1 In summer Lemna shows an excellent effect in 6 days. 

 D. A. 3 



