Rate of Absorption of Various Salts by Plant Tissue. 



487 



Plate 12. — The coloured Plate. 



Figs. 1-4 are all on the same scale of magnification, and represent characteristic views 

 of the four ingredients described in this paper, as seen in micro-sections of untreated 

 coal, showing their natural colours as seen under the microscope. 



Fig. 1. — Section of fusain. At the top, note portion of a bright coloured spore from the 

 adjacent durain. The bulk of the section is still recognisable or macerated 

 wood fibres, the walls of which are quite black and opaque. 



Fig. 2. — Section of durain. Numerous crushed and partly broken spore coats, ranging 

 from gold to orange colour, and various small fragments are interspersed 

 , with the black granular matrix. 



Fig. 3. — Section of clarain. Tissues of a stem, spores and more or less translucent bodies 

 of various kinds, are mingled. 



Fig. 4. — Section of vitrain. Showing its essential structureless condition. The various 

 shades of colour depending upon the thickness of the section, which is never 

 quite uniform. 



Fig. 5. — Tubes showing the approximate colour and the proportion of debris from the 

 four ingredients after the treatment described on page 477. F, fusain, 

 D, dui-ain, C, clarain, V, vitrain. 



The Comparative Rate of Absorption of Various Salts by Plant 



Tissue. 



By Walter Stiles, M.A., Lecturer in Botany in the University of Leeds, and 

 Franklin Kidd, M.A., D.Sc, Fellow of St. John's College, Cambridge. 



(Communicated by Prof. W. M. BayHss, F.E.S. Received August 30, 1918.) 



Introduction. 



In a previous paper we have dealt with the intake by carrot and potato 

 cells of single salts in different concentrations, and we there considered, 

 especially, the dependence of the equilibrium attained in salt absorption on 

 the concentration of the solution exterior to the tissue. In the course of 

 these experiments dealing with the relation between concentration and 

 intake, it was indicated that the rate of absorption and the position of 

 equilibrium ultimately attained depended also upon the nature of the salt. 

 As, however, experiments with different salts were made with different 

 samples of tissue, we did not consider ourselves justified in laying much stress 

 on the results obtained on account of the variability of different samples of 

 tissue, a difficulty to which attention has previously been called. In the 

 experiments recorded in this paper, we have therefore chosen one concentra- 

 tion and compared the conductivity changes produced in solutions of different 

 salts by carrot and potato cells of the same sample. 



2 Q 2 



