CRITERIA AND METHODS 115 



as well as the points discussed in Sec. 14, it seems that 

 experiments with these salts cannot give any clear idea as 

 to the normal behavior of nutrient salts. 



In a more recent paper Bodenberg (1929) has stated 

 that the objection that lithium salts are not satisfactory 

 for use in experiments on transfer appears to be groundless, 

 because he found that they were not rapidly carried across 

 woody stems of willow varying in diameter from 1 to 5 cm. 

 However, one would hardly expect woody tissues, either 

 alive or dead, to offer no resistance whatever to the cross 

 transfer of salts like those of hthium, and since Bodenberg 

 gives no data comparing the rate of transfer of the lithium 

 ion with that of others, his data are far from convincing. 

 Even if it were found that lithium moved across a woody 

 cyUnder less rapidly than potassium, for example, which is 

 not unlikely, the major criticisms of its use to demonstrate 

 translocation remain. Furthermore, Bodenberg did not 

 even demonstrate that water moved across the stem for he 

 had to supply the shoot with water through a wick. In the 

 illustration he gives (Fig. 1, p. 34) he shows a willow stem 

 10.5 cm. long and 2.5 cm. thick. The root is on the under- 

 side of the horizontally placed stem and the shoot is on the 

 upper side, offset 5 cm. from directly above the root. Since 

 water would not move fast enough from the root to the 

 shoot to keep the latter turgid, a wick was led from a 

 separate vessel of water to the upper side next to the shoot 

 to supply it with water. Under such conditions one would 

 hardly expect even water to move to the shoot from the root, 

 to say nothing of the lithium or any other dissolved substance. 



22. Tests for the Deposition of Solutes Introduced 

 through Cut or Uncut Roots. — The method of adding some 

 substance to the soil solution and subsequently testing for 

 its location in the plant has been occasionally used as a test 

 to indicate the tissues taking part in translocation. This 

 method escapes the criticism that some tissue has been cut 

 open for the plant is, or at least may seem, intact. 



The method has been recently used by Overton (1925) 

 who found that after plants were watered with solutions of 



