2 6 
J. H. Priestley 
low temperatures and soluble to a large extent in boiling chloroform, 
he is inclined to regard as true fats; the other series,melting at higher 
temperatures or even decomposing before melting, or melting at 
lower temperatures after previous saponification, he would identify 
with the anhydride or condensation products of the suberogenic 
acids. But the mixture differs from plant to plant as might be 
expected. It has been possible to confirm one micro-chemical 
observation by macro-chemical methods. Van Wisselingh(i7) de¬ 
scribes the periderm of Salix caprea as remarkably aberrant under 
treatment by his method and notes that it never gives any indica¬ 
tion of phellonic acid. Miss Rea has extracted the ground-up peri¬ 
derm of Salix caprea by Gilson’s method and finds that no potassium 
phellonate at all can be identified in the alcoholic extract after 
saponification. 
Cutin has not been so fully examined as suberin, but it is worthy 
of note that long prior to Gilson’s work, Fremy and Urbain( 7 ) as 
the result of the saponification of cutin (or “cutose” as they termed 
it) had obtained two organic acids that they described as “stearo- 
cutique” and “ oleocutique.” They had failed to identify any alcohol 
with which these acids were combined prior to saponification, and 
had noticed the tendency of these acids under various conditions to 
undergo profound modification in their properties, such as losing 
their solubility in fatty solvents, and in the case of the solid acid 
“ stearocutique ” a rise of melting point. 
These reactions certainly suggest “cutinogenic acids” trans¬ 
formed in the formation of cutin in the same way as suberogenic 
acids are modified in forming suberin. 
Furthermore, cutin, examined by van Wisselingh’s method, can 
be shown to contain no trace of phellonic acid though other “ cutino- 
genic” acids are present; this observation also is supported by some 
preliminary macro-chemical observations made by Miss B. Lee. In 
one case van Wisselingh(i 7 and 18 ) examined at different times the 
cuticle and periderm of the same plant. Ilex aquifolium, and a com¬ 
parison of the results will show that in the same plant the substances 
forming cutin and suberin respectively do not seem to be identical. 
We thus reach the conclusion that suberin and cutin are names 
for aggregates of substances which present certain characters in 
common, suberin being present in the median lamellae of the walls 
of periderm cells and cutin as a continuous layer on the outside of 
the cuticle and in dispersed patches throughout the cutinised 
lamellae below when these are present. 
