On some Methods in Palceohotany . 111 
glasses may be used instead of the china pans, but are not so stable 
and it is by no means pleasant to spill the strong acid solution. 
After a time, varying with different specimens from three or four 
hours to as many days, and depending on the strength of the acid 
and on the material of the leaf, the specimens become clear brown in 
colour. The acid is then decanted off, the specimen is washed with 
water and freed from any surface particles by the use of a fine 
brush. A few drops of ammonia solution are then added, which 
cause the cuticle to become black at first, but which later brings 
about the clearing of the specimen and the solution of the dark 
substances. If the process has been complete a more or less clear 
membrane is left, but care must be taken to separate the cuticles of 
the upper and lower surfaces at this stage, otherwise a clear view 
of neither will be obtained. This separation is usually a matter of 
some difficulty, but may be assisted with needles and by using the 
sharpened point of a match. If the specimen does not become 
clear it may be washed and replaced in fresh acid and the process 
repeated. Some leaves may require treating for a considerable 
time before becoming transparent. The resulting cuticles are 
washed with water and may be stained or mounted directly. I often 
employ as a mountant pure Glycerine in which Zinc Sulpho- 
Carbolate has been dissolved (the latter substance improves the 
optical properties of the glycerine). The slides may be conveniently 
sealed with wax, 1 but if they are to be kept for a long time a coating 
of gold size should be added to prevent the wax from cracking. 
Preparations made in this way often yield a surprising amount 
of information about the form of the epidermal cells, the shape and 
distribution of the stomata. If hairs or papillae were present, they 
are clearly seen, while portions of the more resistent sub-epidermal 
tissue, fibres, etc., may occasionally be found. It seems probable 
that the study of the stomata may be useful not only in classifying 
the fronds from which they are obtained, but also in investigating 
their relationships and phylogeny. 
The Study of Sporangia and Spores. 
Careful search in fine grained fossiliferous shales often results 
in the discovery of fertile specimens of ferns, conifers, etc. The 
sporangia of ferns are often quite clearly preserved though con¬ 
verted into carbonaceous material, and the annulus, if present, can 
be clearly seen. The prismatic binocular microscopes made by 
i See New Phyt., Vol. X, p. 105, 1911. 
