to the Plant Cell . 
503 
sand cultures succeeded better when both potassium and sodium were 
present than when only potassium was furnished. Dassonville (’98), who 
studied the effects of various elements upon the form and structure of 
plants, found that wheat plants were strongly lignified at the base of the 
stem when sodium was substituted for potassium. He believed that 
potassium retards the lignification of the mechanical tissues, and that 
sodium, playing a less active role, is less favourable for growth and more 
favourable for lignification. Sodium was less favourable than potassium 
for the formation of secondary roots of the tomato. When sodium was 
furnished the number and importance of the vascular elements in the 
epicotyl were diminished, the cells of the cortex were larger and the 
intercellular spaces smaller. 
Wheeler (’05) has shown that the addition of sodium salts to a soil 
already fertilized with a greater or less amount of potassium salts increased 
the growth of such plants as beets, radishes, and flat turnips, but did not 
increase the growth of rye, chicory, carrots, spinach, and lettuce. The 
continued application of sodium salts in the absence of any potassium salts 
was not generally beneficial. 
The foregoing investigations indicate that there may be functions 
which either sodium or potassium may perform, and other functions which 
only potassium may perform. Such investigations are unfortunately open 
to one serious objection because conducted in soil or sand cultures. The 
soil, like any finely divided solid, possesses specific powers of absorption, 
and would hold a certain amount of basic bodies (among them potassium) 
in an absorbed state. The addition of sodium salts would tend to liberate 
some of the potassium with consequent benefit to the plant. The soils also 
furnish a certain amount of potassium from the potassium-containing 
minerals which enter into their composition. 
The work of Breazeale (’06) is not, however, open to such criticism 
because conducted in water cultures. Breazeale was successful in measuring 
the amount of different nutrients removed from a complete nutrient solution 
after being transferred from solutions in which some one element was 
lacking. He showed that plants which had previously grown in solutions 
lacking potassium usually withdrew more potassium, in proportion to their 
growth, from the complete nutrient solution than plants of the same age 
which had previously grown in a complete nutrient solution. Plants which 
had previously grown in solutions lacking sodium also absorbed more 
potassium than those previously grown in complete nutrient solutions 
containing both sodium and potassium. Finally he showed that plants 
which had previously grown in solutions lacking both sodium and potassium 
drew most heavily upon potassium when placed into complete nutrient 
solutions. These results, more than any others known to the writer, 
appear to give definite facts upon which the question of the possible value 
