io4 
/?. C. McLean. 
emphatically to the need of this care in preservation, since the 
possibilities of future study are strictly limited by the preliminary 
treatment. Where dry specimens are easily revived, much time 
and trouble may profitably be diverted from wet preservation and 
devoted to the improvement of the drying method. 
Two methods which have been previously employed for 
resuscitation are quoted by Zimmermann (2), involving the use of 
Lactic Acid (3) or a mixture of this with Phenol. For some 
extremely delicate structures the first of these may be of some 
value, but a somewhat extended trial of it on herbarium specimens 
of Rhodophyceae from Harvey’s Australian collections has given very 
unequal results. The cell-walls of tissues which have been for a 
long time dry—a decade or upwards—appear to acquire a species 
of rigor which it is very difficult to break down. In other words 
the gel colloids of the walls lose part of their reversibility, and 
become to a certain extent incapable of reimbibition or at least of 
hydrosolution. 
Where this condition is very pronounced Lactic Acid is power¬ 
less to rectify it. Such is markedly the case where there has been 
mechanical distortion during drying, or a very large percentage of 
shrinkage in volume. 
The admixture of Phenol is a partial but not complete 
amelioration, and as the relatively slight solubility of this reagent 
makes it difficult to wash it out of a bulky organ, it has compensa 
ting disadvantages where subsequent dehydration is an object. 
For the treatment of some algae, or of objects accidentally 
dried for short periods, or of very minute objects, the above quoted 
methods may however be useful, and they lend themselves especially 
to the making of glycerine jelly mounts. 
The method which 1 wish to describe is adapted to such cases 
as are not covered by the above methods, namely bulky, hard or 
resistant structures, or such as have undergone great change of 
form in drying. At the same time I would emphasise that it is 
equally applicable to the case of delicate organs, and will, if used 
with care, give results superior to those obtainable with Lactic Acid. 
If the precipitation of the hydrogels which go to form the cell- 
wall has entered upon a state of quasi-permanence, no acid medium 
which does not at the same time cause solution will effect the 
desired change. Alkalis are more effective, and for the purpose 
in view I have had recourse to the old fashioned Potash. 
