258 J. H. Priestley and L. M. Woffenden 
water there was slight suberisation of the outer layer of collen- 
chyma but no trace of a meristem. 
The absence of a meristem suggested to us incomplete blocking 
of the exposed surface in contact with the water. This might be due 
to the products which accumulated at the surface in the air, diffusing 
under the experimental conditions into the water. In each experi¬ 
ment the water changed each day was collected and kept. At the 
end of the experiment it was evaporated down and the residue in 
the evaporating dish extracted with boiling chloroform. The chloro¬ 
form extract, filtered and evaporated, left a little amorphous waxy 
deposit which stained yellow brown with iodine. Treated with 
iodine and dilute sulphuric acid, part of the substance gave a reddish 
reaction very reminiscent of phellonic acid (see Priestley (20) for an 
account of the organic acids present in suberin). After saponification 
with boiling alcoholic potash, the residue from evaporation of the 
water was again evaporated to dryness and taken up with boiling 
chloroform. A much larger quantity of the residue now went into 
solution and this substance after evaporating off the chloroform 
again gave the phellonic acid reaction. As however the residue in 
part dissolved in ether, in which phellonic acid is insoluble, it cannot 
be entirely composed of phellonic acid, and the ether soluble con¬ 
stituent also gave a reddish violet reaction with iodine and sulphuric 
acid. These reactions suggest then that there had diffused from the 
injured surface into the water substances which, like the suberogenic 
acids, were soluble in fatty solvents, and which also were partly 
present as condensation products, insoluble in fatty solvents without 
previous saponification. At the surface exposed in air the accumu¬ 
lation of these substances may well be responsible for the stronger 
and more widely distributed suberin reaction. 
In these experiments with begonia we obtain evidence again that 
periderm formation involves two processes, first a suberisation which 
seals the injured surface, secondly a meristem formation which 
follows upon the accumulation of sap at the injured surface. If a 
plant is taken which unlike begonia has a secondary endodermis in 
the stem, this will completely retain the sap pressure within it 
(Priestley and North (22)). A superficial wound should then be fol¬ 
lowed by suberisation without subsequent meristem formation. 
Experiment shows that facts are in accordance with this expectation. 
The stem of Camellia japonica L. has a strongly developed secondary 
endodermis, in which all walls are suberised. The young stem has a 
clear green cortical tissue outside the endodermis. Superficial cuts 
