“…A portion of the solution was first run through and thrown away, to avoid the effect of adsorption of the dye by the asbestos. After filtration, the sample was tested for the amount of dye remaining in solution in a Leitz bicolorimeter, following the conventional procedure (1). In most cases it was possible to obtain a good match of colors without resorting to a second wedge containing a distilled-water extract of the plant tissue.…”