Permeability 145 
equation, Sziics concludes that the extent to which the intake of dye 
is prevented depends on the adsorption of electrolytes by the proto¬ 
plasm. 
Further investigations on this question have been made by 
Endler (1912 a) who used only truly soluble dyes, particularly 
methylene blue, but also neutral red. Among the species employed 
were Ulva lactuca, Nitophyllum punctatum, Spirogyra spp. and Elodea 
densa. Endler’s results deviated somewhat from those of Sziics. With 
a large number of chlorides and sulphates added singly to a solution 
of dye, he found that the rate of intake of dye was increased with 
increase in the concentration of the electrolyte present, but with 
further increase in concentration of the electrolyte the intake of dye 
decreased. Thus, with Elodea densa in a solution of 0-05 per cent, 
neutral red it was found that the maximum intake of dye took place 
when the chloride or sulphate of a number of metals was present in 
a concentration between o-oi M and 0-05 M. Similar results were 
obtained with methylene blue, with which the order of inhibiting 
action of different salts was as follows: salicylate (complete pre¬ 
vention of dye intake with o-ooi M), aluminate (complete prevention 
of dye intake with o-oi M) [citrate, tartrate], [chloride, sulphate], 
nitrate (recognisable uptake of dye with 0-4 M). Little difference was 
observed between the different salts of the same anions, with the 
exception that aluminium salts hinder the intake of dye more 
significantly than other salts examined. 
Where the results of Sziics and Endler diverge, the explanation 
may be found in the fact that Sziics observed the time taken for a 
certain quantity of dye to be absorbed, while Endler was concerned 
with the total quantity of dye absorbed at equilibrium. Also the 
materials, both dyes and plant species chiefly used, were different in 
the two sets of experiments. 
The action of a number of substances in influencing the intake 
of sulphonic acid dyes by perianth leaves of Hyacinthus has been 
examined by Collander (1921). He found the intake of cyanol and 
orange G was strongly hindered by a 2 per cent, solution of ether, 
although a 1 per cent, solution had only a little influence, while 
solutions containing 3 per cent, ether or more killed the cells in a 
short time. Chloral hydrate in concentrations from 0-5 to 1 per cent, 
also inhibited the intake of the dye, while 2 per cent, killed the cells 
in a short time. 
Collander, using dyes in presence of phosphate mixtures of 
definite hydrogen-ion concentration, concluded that the hydrogen- 
Ph vt. xxii. 3. 10 
