438 Dr. F. A. Bather—Collodion Imprints of Fossils. 
applied the method to the study of the surface structure in fossil 
plants. It is, however, to Professor Nathorst that we are indebted 
for the first publication of results obtained by it in the study of 
fossils,‘ and for the first account of its advantages in palobotany. 
From the many instances of the successful use of this method given by 
Professor Nathorst a few will now be noticed. 
The first attempt was naturally one to study well-preserved cuticles 
of carbonised leaves. In the case of Bavera spectabilis, however, 
a ginkgo form from the Coal-measures of Scania, the attempt was 
quite unsuccessful. In the case of some carbonised leaves of 
dicotyledons it was occasionally possible to observe a suggestion of 
the contours of the elongate cells over the veins and their branches ; 
but this was of no particular interest. 
Fre. 1. —Microphotograph (x 500 diam.) of a collodion film showing a stoma and - 
the outer sculpture of the cell-membrane on the upper suriace “ot a leaf of 
Tussilago farfara in the calcareous tufa of Benestad in Scania. (Lent by 
Geologiska Féreningen i Stockholm.) 
Better results were obtained with the sporangia of fossil ferns. In 
his description of Dictyophyllum exile last year, Professor Nathorst 
was able to publish photographs of those organs enlarged 8 diameters ; 
but the use of films enabled him to study the same bodies with the 
microscope, aud he now reproduces a photograph enlarged 45 diameters. 
Fossil sporangia are best studied by this method when they have 
a well-developed annulus, but good imprints have also been taken 
from the sporangia of Zodztes Williamsont i in which this is not the case. 
Occasionally some sporangia adhere to the collodion film and are 
pulled away with it. This was the case with a specimen of Zhaumatop- 
teris Schenki. By laying the film in Eau de Javelle the walls of 
the sporangia were dissolved, and the spores, adhering to the film, 
exposed in their undisturbed position (op. cit. ult., 1907, pl. ui, fig. 18). 
1 «Ueber Thaumatopteris Schenki Nath.’?: K. Sy. Vetenskaps-Akad. Handl.,, 
xlii, No. 3, 1907. 
