384 Walton.—On a New Method of investigating Fossil 
I. Psilophyton princeps. Dawson. 
Locality : Callendar, Perthshire. Horizon : Lower Old Red Sandstone. 
The transfer preparation of a specimen of Psilophyton princeps figured 
in PI. IX, Fig. 12, at once reveals the presence of a considerable amount of 
the original organic substance of the plant. It will be seen on examining the 
figure that the stem is studded with small spine-like emergences which are 
somewhat irregularly placed over the surface of the plant exposed by this 
method of preparation. It is possible that some have been knocked off, and 
that they are therefore not completely represented. It is hoped that further 
preparations may give more reliable information as to their arrangement on 
the stem. The general form of the emergences can be made out at the top 
of Fig. 12. They are somewhat expanded at the base and are flattened in 
a radial plane (with reference to the axis of the plant). On examination 
by transmitted light they were found to be transparent and brown in 
colour and probably represent the cuticularized portions of the original 
emergences. 
It is worth noticing that these spinous structures seem to be better 
preserved than the rest of the plant represented in the fossil. This is 
probably due to the greater proportion of cuticularized material in them, 
and seems to me to suggest that they were probably not structures repre¬ 
senting an extension of the area of photosynthetic tissue, and that if they 
had any function at all it was of a mechanical nature. We know from the 
researches of Kidston and Lang 1 that the Rhynie plants which are included 
in the same group (Psilophytales) as Psilophyton had well-developed 
cuticles on the stems. 
II. Mariopteris , cf. muricata , Schloth., sp. 2 
Horizon: Carboniferous. 
I am indebted to Mr. Hamshaw Thomas for calling my attention to 
the work of Huth 2 on the foliar epidermis of Mariopteris muricata , in which 
air pores (‘Atemporen’) comparable in structure to those of Marchantia 
are described. Mr. Thomas suggested that a structure which occurred on 
the epidermis of a specimen of Sphenopteris nummularia (to be described 
later) resembled the air-pores described by Huth very closely. Huth 
mentions that Haberlandt, objecting to his theory of the nature of the 
Atemporen, suggested that they might be hair-bases. As stomata of quite 
usual type were found on Sphenopteris nummularia , the suggestion that 
these ‘ Atemporen ’ might really be the points of insertion of hairs or 
emergences of the epidermis seemed possible. More recently Gothan 4 
2 Dr. Kidston very kindly identified this specimen. 
4 Gothan, W. (1915). 
1 Kidston and Lang (1917), p. 769 . 
8 Huth, \V. (1913), Fig. 3, p. 16 . 
