18 J. H. Priestley 
isolated and described and a suggestion can be made as to the form 
in which they are present within the wall. Furthermore, the ground 
seems clear for future work which may be expected to elucidate the 
nature and origin of the substances in the cell from which suberin 
and cutin are first formed, and also the conditions under which pro¬ 
ceeds the transformation of these substances into suberin and cutin. 
The following account is written with the more confidence because 
practically all observations which the present writer regards as 
fundamental have been repeated in his laboratory by different 
students. In this connection he has particularly to thank Miss 
M. Hind, B.Sc., Miss Edith North, B.Sc., Miss R. Rea, B.Sc., and 
Miss B. Lee. 
Towards a Definition of Suberin —A Comparison with Lignin 
The term suberin is due to Chevreul(2) and was given by him to 
a substance insoluble in water and alcohol and constituting seventy 
per cent, of the substance of bottle cork. This substance he regarded 
as responsible for the special properties of cork, impermeability to 
water, general insolubility and great resistance to acids, etc. 
“Suberin” starts in the literature then as a substance generally 
responsible for the peculiar properties of cork, and it appears to 
have gained little in clearness in English botanical literature until 
the present time. The reason for this is easily seen. Most botanical 
investigations have followed the micro-chemical method in investi¬ 
gating cork. Naturally it has not been possible to get much further 
than that the substance which appears to give cork tissue or peri¬ 
derm its peculiar properties, is concentrated in a special lamella 
constantly present within the cell wall of the cork cell. To this 
substance or mixture of substances the name of suberin has been 
given by common consent. 
The first full and clear description of the substance or substances 
in the lamella we owe to von Hohnel( 9 ) whose work remains a land¬ 
mark in the study of the subject, and it will be useful to cite briefly the 
characteristics of suberin as recognised in von Hohnel’s monograph. 
One difficulty has always been to distinguish suberin from lignin, 
as both lignified and suberised tissues are left behind by treatment 
with strong acids or cellulose solvents. Von Hohnel points out that 
lignin possesses many more characteristic colour reactions, a state¬ 
ment which is even more true to-day when beside those with phenol 
acid salts, many more general colour reactions for lignin are known. 
(See Czapek( 4 ), p. 689.) 
