is poured over the ‘‘etched’’ surface and permitted to 
dry. The dried film is carefully peeled off. The proce- 
dure may be repeated many times. 
In addition to this method of making multiple peels 
from one specimen, paleobotanists, since the time of 
Nathorst, have ‘‘transferred’’ various types of carboni- 
zations and incrustations. Walton’ has fully described 
this method. The thin, but nevertheless three-dimension- 
al fossil is cemented to a glass slide with collodion or bal- 
sam. Then the glass slide is covered completely with 
paraffin. Finally the specimen is placed in a container 
of hydrofluoric or nitric acid and allowed to remain in 
the acid until all mineral has been removed. Obviously 
this process is very slow. 
For the past five years various experiments have been 
made with the result that these two types of work can 
be done with one simple, time-saving technique. Im- 
proved solutions have been developed to aid in the prep- 
aration of satisfactory peels. 
The possibilities of microtechnique in paleobotany 
have not been recognized, or even admitted by many 
botanists and geologists. Nevertheless, the trained pa- 
leobotanist can obtain through microtechnique the max- 
imum available information from any specimen with pre- 
served structure. Even the simple carbonized impression, 
long considered worthless as a source of biological data, 
may be studied without difficulty by the peel method. 
The complete process of making a nitrocellulose peel 
involves a number of steps. These are in order: grinding, 
etching, drying, smearing, peeling, and care of peels. 
Grinding. Any petrified specimen in which chemical 
replacement has occurred may be studied by the prepara- 
tion of multiple peels (or serial-sections). It is necessary 
6 . 
loc. cit. 
[70 | 
