THE ROOT 185 
now we repeat the same experiment with the addition of coloring 
the sugar solution with eosin, the sugar solution still rises in the 
tube while some of the eosin passes out through the parchment 
paper and colors the distilled water. In other words, the move- 
ments of the eosin and the water are independent. 
Accumulation of mineral matter in a plant. As movement by 
diffusion is always from a greater to a less concentration, a given 
kind of mineral matter would be expected to enter a plant only 
so long as the concentration of that particular substance was 
greater outside than inside the plant. The original substance, 
however, after entering a plant, is usually combined with others 
in such a way that it no longer exists in the same form as in 
the soil water. In this way the concentration of a given sub- 
stance may remain greater outside than inside, even though it 
is absorbed in large quantities. Owing to this fact a plant may 
accumulate a much greater proportion of a given element than 
is found in the soil water. | 
As the diffusion of mineral matter dissolved in water is in- 
dependent of the diffusion of the water itself, an increase in 
the amount of water absorbed by a plant would not increase 
the amount of mineral matter absorbed if the water moved in the 
plant only by diffusion. It is only owing to the fact that the 
water in the vessels moves as a steady stream, and not by diffu- 
sion, that transpiration can increase the amount of mineral mat- 
ter taken in by a plant. 
It is indeed questionable how far transpiration can cause an 
accumulation of mineral matter in a plant. If any given mineral 
substance should accumulate anywhere in the plant in greater 
concentration than it occurs in the soil, it would tend to diffuse 
to a region of lower concentration and finally to the soil water. 
It is only as a given mineral substance is changed into some 
other substance that the elements composing it can accumulate 
in the plant to a much greater extent than that in which they 
occur in the soil water. 
