28 TRANSLOCATION. [CH. II 



In the evening a similar process is gone through with 

 the control halves. The following is the result of one of 

 Sachs' experiments. A hundred sq. cm. were cut out of 

 the halves of 7 leaves of Helianihus annuus ; the dry 

 weight of the 700 sq. cm. was : — 



5 a.m. 3'0o4 grams. 

 3 p.m. 3-693 „ 

 •639 „ 

 This equals 0'9 grams per sq. meter of leaf surface, per 

 hour. 



Mutatis mutandis the weighing method is used by 

 Sachs for showing the loss by translocation in the night. 



(37) Translocation. 



Sachs' iodine method is also useful, for studying the 

 translocation of carbohydrates, i.e. that the products of 

 assimilation wander from the leaf to the body of the 

 plant'. 



In the evening remove the halves of several leaves and 

 having tested small pieces of each (which should be 

 preserved for further comparison) place the freed halves 

 on wet filter-paper under a bell-jar in a dark room ; the 

 plant must also be placed under a bell in the same room. 



In the morning the half-leaves attached to the plant 

 will have lost more starch than the free halves. 



(38) Assimilation of Sugar. 



Water-plants, such as Elodea or Potamogeton, are 

 placed in vessels of 400 or 500 c.c. capacity, containing 

 spring water, to one of which (A), 3°/^, cane sugar has 

 ' More accurate methods are described in Fart n. Chaps, ^ii. and xiv. 



