I TO 
H. Hamshaw Thomas. 
have inspired in the minds of many, a profound distrust for much 
of the work based on the study of impressions. But where the latter 
can he correlated with petrifactions or some knowledge gained of 
their structure, a comprehensive study of their external form may 
be of the greatest importance. In the case of mummified plants or 
of impressions in which the plant substance is not entirely destroyed, 
much information can usually be gained as to the form of the 
stomata, epidermal cells, spores, seeds, etc., by the use of suitable 
methods. This is especially the case with those Mesozoic plants 
which are preserved in fine shales or mudstones ; the tissue has not 
yet become completely carbonised, and the remains of the plant 
can usually be easily detached from the matrix. These plants are 
especially worth study because we know of so few localities in which 
petrifactions of this age are found, and hence we have comparatively 
little knowledge of the affinities of many Jurassic plants, at the same 
time they are the key to many of the most discussed phylogenetic 
problems. In these circumstances a close study of the remains 
which have hitherto been regarded as structureless may lead to 
interesting results. 
The object of these notes is to give a brief account of some of 
the methods which have proved useful in studying Jurassic plants, 
chiefly of the mummified or impression type. 
Preparations of Leaf Cuticles. 
These can be readily made from specimens of plants which 
originally possessed a fairly thick cuticle and which are preserved 
in a fine grained matrix from which they can be easily detached. 
It was shown by Borneman in 1856 that the carbonaceous material 
could be dissolved out by using Schultz’s solution, and the method 
has since been used with considerable success by Schenk, Zeiller, 
Nathorst and others. 
The following method may be employed. A portion of the leaf 
is chosen in which the tissue shows a tendency to peel off, and some 
of it is removed with a needle. If a drop of water is previously 
placed on the spot, it often renders the removal of the tissue easier. 
The detached fragment is then placed in a shallow china pan of the 
type used by artists for mixing water-colours (these pans are circular 
and are made in sets, one fitting on top of another and acting as a 
cover), a little powdered Potassium Chlorate is sprinkled on it 
and a few drops of moderately strong Nitric Acid added. The pan 
is covered up, labelled, and left to stand for some time, Watch- 
