190 
W. H. Pearsall and J. H. Priestley 
been made out for considering many well-known facts of plant 
anatomy from the following standpoint: 
Synthetic metabolic processes are usually condensations involving 
the release of water from the reacting substances. As reversible 
reactions, such synthetic processes are therefore facilitated by the 
removal of water from an actively synthesizing (or growing) meri- 
stem. Hence the fact that the cambial meristerns lie across gradients 
of hydrogen-ion concentration suggests that they occur at that 
point where important constituent proteins are at their iso-electric 
point. These proteins thus possess minimal affinity for water, which 
may, therefore, be withdrawn from the meristem to the osmotically 
active cells on either side. An examination of the iso-electric points 
of tissue proteins so far as these are known suggests that the majority 
of such proteins have iso-electric points lying within the range of 
hydrogen-ion concentration observed on the two sides of a cambial 
meristem. 
These correlated data are at least suggestive and in the case of 
the cork phellogen no other causal mechanism has been suggested, 
so far as the writers are aware, which gives an adequate basis for 
the production of a new meristematic unit within an originally 
vacuolated cell. A moment’s consideration will show that the same 
mechanism would account for the development of a cambium within 
the procambial strand and its gradual extension as interfascicular 
meristematic tissue across the primary medullary ray. The problem 
of the apical meristems has been left on one side in this paper as it 
presents additional difficulties in observation and interpretation. 
There seems to be little doubt that here also water is withdrawn 
from the meristem in a somewhat similar way, although the manner 
in which the meristem proteins are maintained at the iso-electric 
point is not at present clear. 
REFERENCES 
(1) Atkins, W. R. G. ( The Hydrogen-ion concentration of plant Cells. Scient. 
Proc. Roy. Dub. Soc. 16 , pp. 414-426. 1922. 
(2) Bayliss, W. M., Principles of General Physiology (2nd ed.). London, 
1918. 
(3) Bourquelot, E. and Bridel, M., Synthese des Glucosides d’alcools a 
l’aide de l’emulsine et reversibilite des actions fermentaires. Ann. de 
Chim. et Phys. 28 , pp. 145-221. 1913. 
(4) Burton, E. F., The Physical Properties of Colloidal Solution. London, 
1916. 
(5) Clarke, The Determination of Hydrogen Ions. Baltimore, 1920. 
(6) Hardy, W. B., Colloidal Solutions: the Globulins. Journal of Physiology , 
33 , p. 251. 1905. 
