Suberin and Cutin 
23 
It thus appears that it is possible to prepare artificially condensa¬ 
tion products of these suberogenic acids and their salts which have 
the reactions that have been cited as characteristic of suberin; and 
that these acids can be obtained from suberin by saponification. The 
conclusion is then rendered probable that suberin consists largely of 
anhydrides of these acids, possibly together with a small proportion 
of the acids combined with glycerine as glycerides or true fats. 
Von Hohnel, and Fremy(6) before him, spoke of suberin and cutin 
as definite individual substances, but it is obvious in the light of 
Gilson’s work that they are more probably aggregates or mixtures 
differing in their composition with variations in the original pro¬ 
portions of the suberogenic acids from which they are formed. 
This is indeed the case, for Gilson himself showed that the cork 
of Ulmus “suberosa” differed in its constituent suberogenic acids 
from that of Quercus suber, phellonic acid, present in considerable 
quantities in the cork of the latter being quite absent from that of 
the former. 
Possibly these suberogenic acids may have a practical future 
before them in water-proofing cellulose fabrics (see Cross and 
Bevan( 3 ), loc. cit. p. 235). Certainly they exist in nature in sufficient 
quantities if they are required; the Eriophorum peat deposits of 
Yorkshire consist largely of the preserved cuticle, endodermal and 
corky tissues of Eriophorum and some preliminary experiments by 
Miss Hind show that large quantities of these suberogenic acids can 
be readily obtained from this peat by saponification. 
Micro-Chemical Investigations —No Cellulose Basis to 
Suberin or Cutin Lamella 
For the clear recognition of the difference between cutin and 
suberin, and between the suberin of different species, we must turn 
to van Wisselingh’s papers ( 15 - 18 ). 
Van Wisselingh’s methods need studying in the original papers, 
and show how much insight into the ultimate structure of the mem¬ 
brane can be obtained in spite of the limitations of micro-chemical 
technique. The basis of this method was a study of the progressive 
decomposition or melting of the suberin lamella under four different 
methods of treatment: (1) heating in pure glycerine over a range of 
temperature, the highest well above 300° C., (2) heating in glycerine 
after previous treatment in concentrated potash (50 per cent.), 
(3) heating over the same range of temperature in glycerine contain¬ 
ing 10 per cent, potash, (4) warming in 10 per cent, alcoholic potash. 
