D. Thoday. 
57 
SOME OBSERVATIONS ON THE BEHAVIOUR OF 
TURGESCENT TISSUE IN SOLUTIONS OF 
CANE SUGAR AND OF CERTAIN TOXIC SUBSTANCES. 
By D. Thoday, M.A. (Cambridge). 
[With Eight Figures in the Text] 
HE experiments described in this paper were made several 
years ago in the course of investigations on the effect of 
anaesthetics and other toxic substances on respiration. They were 
suggested by A. J. Brown’s remarkable observations on the selective 
permeability of the coat of the barley grain and the influence 
of different solutes on the rate of entry of water into the grain . 1 
Pieces of potato were put into various solutions and their gain or 
loss in weight followed in order to see whether the behaviour of 
this very different material corresponded with that of barley grains 
in solutions of the same substances. 
The structure of the material made the problem a more 
complicated one than that which Brown was investigating. In the 
case of the barley grain the whole grain forms a single “ cell,” 
enclosed in a membrane which is chemically and mechanically 
very resistant. Brown and his collaborators have therefore 
been able to formulate their problems in relatively simple terms,, 
viewing the dry seed “ as a diffusion system consisting of a mass 
of solid material capable of absorbing moisture enclosed within a 
differentially permeable membrane.” 2 
Lately they have summed up their earlier work as follows: 
“ Previous results . . . have demonstrated that when seeds of 
Hordtum are immersed in solutions of solutes to which the seeds 
are impermeable, less water enters the seeds than from pure water, 
and that the actual amount entering is regulated, in the main, by 
the osmotic pressure of the solution in which the seeds are 
immersed . . . On the other hand . . . that with solutions of 
those solutes which are able to diffuse through the seed membrane 
there is a general tendency not only for more moisture to enter the 
seeds than from pure water itself, but also for the rate of entry of 
the moisture to he accelerated to an extent varying with both the 
nature of the solute and the concentration of its solution .” 3 
The outstanding questions clearly relate to the causes which 
determine on the one hand the degree of permeability of the 
1 Proc. Roy. Soc., B. 81, 1909, p. 82. 
1 Brown and Tinker, Proc. Roy. Soc., B 89, 1915, p. 119. 
3 Loc. cit., 1915, pp. 119-20. 
