128 THE MECHANISM OF ABSORPTION AND TRANSLOCA TION 



In these analyses the relatively great accumulation of iodine may be noted, 

 since sea-water contains less than 0-00,0001 per cent, of iodides 1 . 



Forchhammer 2 found only a trace of manganese in the ferric oxide obtained 

 from about twenty pounds of sea-water. The ash of the marine alga Padina 

 Pavonia contains, however, as much as 8-19 per cent, of manganese (total ash, 

 34'75 P er cent.). In Sects. 73 and 75 mention is made of the fact that, in addition 

 to manganese and silica, other non-essential elements may accumulate in certain 

 plants to a marked extent. 



The following analyses, made by Gorup-Besanez (Wolff, I.e., p. 133), of 

 unattached floating plants of Trapa nafans, show how ash constituents may be 

 absorbed in percentage amounts differing from those in the water in which the 

 plant is growing, and they also show how the percentage composition varies in 

 different stages of development and in various parts of the plant, not only as 

 regards the total amount of ash, but also as regards its percentage composition. 

 The percentage of ash to dry substance and the percentage amounts of the indi- 

 vidual constituents present in the ash are tabulated. Whole plants were taken for 

 analysis from the same locality, one set in May and another in June. Pericarps 

 also were analyzed, but these had unfortunately been immersed in water since 

 the previous year. Ten thousand parts of the water contained 0-8044 f asn > the 

 percentage composition of which is given beneath. 



De Saussure 3 long ago had recognized that the composition of the ash of a 

 particular plant might be markedly influenced by the nature of the soil on which it 

 was growing. As is shown by water cultures, the degree of concentration of the 

 whole fluid, or even of one constituent, may produce perceptible and often very 



1 Liebig,!. c., pp. 73, 525. 



a Forchhammer, Ann. d. Phys. u. Chemie, 1855, Bd. XCV, p. 84. 



' Saussure, Rech. chim., 1804, Tables d'incinerations, No. 67 seq. See also Wolff. 



