32 TRANSLOCATION. [CH. II 



the halves of 7 leaves of Helianthus annuus', the dry 

 weight of the 700 sq. cm. was : 



5 a.m. 3*054 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 cool 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. We have 

 found Sparmannia give a good result when darkened from 

 5 p.m. until 10.30 a.m., the half-leaves attached to the 

 plant being starchless and contrasting well with the free 

 halves. 



(38) Assimilation of sugar*. 



Water-plants, such as Elodea, Potamogeton, Lemna, 



1 More accurate methods are described in Part n. Chaps, xiii. and xiv. 



2 Bohm, Botan. Zeitung, 1883 ; Meyer, Eotan. Zeitung, 18S6 ; Acton, 

 Proc. Eoyal Soc. Vol. 47. 



