386 Walton. - —On a New Method of investigating Fossil 
considered as projections from subsidiary cells surrounding the stoma, which 
was slightly sunk below the surface. There were at least seventy-five 
stomata per sq. mm. As an argument against considering the £ Atemporen’ 
as hair-bases, as Haberlandt suggested, Huth writes: ‘ Ich habe eine recht 
grosse Anzahl von Mariopteris mnricata-l^estQn in der Hand gehabt, und 
habe nie, weder mit blossem Auge, noch mit der Lupe, noch mit dem Bino- 
kularmikroskop jemals Harchen entdeckt.’ This example serves to stress 
the fact that the exposed surface of a fossil plant has almost always been 
stripped, by the splitting of the rock, of any emergences it may have borne. 
III. Cladotheca undans, (Halle) Lind, and Hutt. sp. Jurassic Estuarine 
Beds, Gristhorpe Bay, Yorkshire. 
As an example of the way in which this method can be employed in 
the investigation of fertile fronds, I give the results obtained by examination 
of a specimen of the above fern. Halle 1 gives a schematic figure of the dis¬ 
position of the sporangia on the specimens he investigated. As both his 
specimens had been exposed by splitting open the shale in which they had 
been embedded, an inaccurate idea of the character of the sorus is given. 
The sporangia are described as forming two rows, one on each side of 
a linear placenta, which was probably superimposed over a lateral vein of 
the pinnule. This apparent arrangement is due to the fact that only the 
sporangia which lay next to the surface of the lamina are visible (Text- 
fig., 3 and 3 a). Halle'says: ‘In places where the coal’ (presumably the 
material of the lamina) ‘ has been removed, both specimens show fairly 
clearly the arrangement and structure of the sporangia.’ 
The split in the shale has occurred over the upper surface of the leaf 
(Text-fig., 2), and where the material of the lamina has disappeared (Text- 
fig., 3 and 3 a) the sporangia, which were actually in contact with its 
under surface, can be seen (Halle, 2 PI. II, Fig. 2), but those sporangia which 
arose from the placenta at right angles to the under surface of the leaf are 
embedded out of view in the matrix. 
When a transfer preparation (PL IX, Fig. 7) was made from a specimen 
collected in 1922 at Gristhorpe, the sori were found to be superposed on the 
lateral veins of the pinnule (Text-fig., 4), extending from close to the 
main vein of .the pinnule to near the lobed margin of the latter. The 
sporangia formed a dense covering (Text-fig., 4 a), and only in places 
where they had presumably fallen off was it possible to see the underlying 
sorus or vein. It has been already mentioned that fossil plants when 
detached from the rock may be partially transparent. This type of fossiliza- 
tion is quite common, although in the majority of examples the plants are 
too fragile to be detached wholesale by mechanical means, such as were 
1 Halle, T. G. ( 1911 ), p. 6, Fig. 1. 
2 Ibid. (1913), loc. cit. Cf. PI. IX, Fig. 2 . 
