470 



Dr. M. C. StoppiS. On the Four Visible 



(8) Nathansohn, A. " Weitere Mitteilungenluber die Eegulation der Stoffaufnahme, 



' Jahrb. "Wiss. Bot.,' vol. 40, pp. 403-442 (1904). 



(9) Pantanelli, E. " Uber lonenaufnahme," 'Jahrb. Wiss. Bot.,' vol. 56 (Pfefifer 



Festschrift), pp. 689-733 (1915). 



(10) Ruhland, W. "Zur Frage der lonenpermeabilitat," 'Zeitschr. f. Bot,' vol. 1, 



pp. 747-762 (1909). 



(11) Stiles, W., and Jorgensen, I. " Studies in Permeability. I. — The Exosmosia of 



Electrolytes as a Criterion of Antagonistic Ion-Action," ' Ann. of Bot.,' vol. 29, 

 pp. 349-367 (1915). 



(12) Stiles, W., and Jorgensen, I. "Studies in Permeability. TV. — The Action of 



various Organic Substances on the Permeability of the Plant Cell, and its Bearing 

 on Czapek's Theory of the Plasma Membrane," ' Ann. of Bot.,' vol. 31, pp. 47-76- 

 (1917). 



(13) Stiles, W., and Jorgensen, I. " Studies in Permeability. V. — The Swelling of Plant 



Tissue in Water and its Relation to Temperature and various Dissolved Sub- 

 stances," ' Ann. of Bot.,' vol. 31, pp. 415-434 (1917). 



(14) Troendle, A. " Sur la Permeabilit6 du Protoplasme Vivant pour quelques Sels, 



'Arch. Sci. Phys. et Nat.,' vol. 45, pp. 38-54, 117-132 (1918). 



(15) Wodehouse, R. P. " Direct Determinations of Permeability," ' Joum. Biol. Cbem.,^ 



vol. 29, pp. 453—458 (1917). 



On the Four Visible Ingredients in Banded Bituminous Coed r 

 Studies in the Composition of Coal, No. 1. 



By Marie C. Stopes, D.Sc, Ph.D., Fellow and Lecturer in Palaeobotany 



University College, London. 



(Communicated by Sir George Beilby, F.RS. Eeceived August 22, 1918.) 



[Plates 11 and 12.] 



Even after a century of investigation coal remains a complex mass of which- 

 the component parts can neither be handled nor separately identified. Many 

 authors have recognised a variety of plant remains in coal, and the specific 

 identification of these organisms and tissues has made good progress ; but 

 such work is truly palaeontological, and the points of interest in it are the 

 organisms and not the coal mass of which they form a part. 



From another point of view coal is a rock, but, unlike most rocks, the 

 nature and orientation of its component parts are scarcely known. One of 

 the most distinguished of living geologists once said to me that he would 

 like to have available about microscopic sections of coal rationalised data 

 comparable with those already obtained by petrologists about thin rock 

 sections. The present paper is a contribution in that direction. It is an 

 attempt to present systematically certain observations made incidentally in 



