378 MR. W. N. EDWARDS ON THE 
(text-fig. 1) and the cuticle shown in Pl. 87. figs. 2, 3, & 6 was taken from it. 
Several other specimens also yielded cuticles, which were sometimes very 
fragile and not well preserved, but in all cases where the structure 
could be made out it agreed with that of the specimen just mentioned. 
When in Stockholm in the spring of 1922, I examined further material from 
Gaspé in the palæobotanical section of the Natural History Museum, by 
kind permission of Prof. T. G. Halle, and obtained good preparations very 
similar to those in the British Museum. 
Before proceeding to describe the specimens in detail, it may be of interest 
to note that this ancient plant has retained its cuticle practically unchanged 
since Lower Devonian times, and that no plant cuticles preserved in this way 
have hitherto been recorded, so far as I am aware, earlier then the Carbon- 
iferous. Like other “ mummified” fossil cuticles, that of Psilophyton takes up 
stains (such as safranin and methyl green) as readily as if it had been 
obtained from a living plant. 
Fig. 9. 
P. princeps. Sketches of stomata from a slide in Stockholm Museum 
(Palæobotanical Section). 
Structure of Epidermis. 
The epidermal cells, which are angular and usually longer than broad, 
vary considerably in size and shape, and PI 37. fig. 3 gives a good idea 
of the variation in a small area. Almost square cells are seen occasion- 
ally, but they are more often fusiform or long and narrow with oblique end 
walls. The actual length of the cells varies from ‘075 mm. to ‘3 mm., and 
the width from ‘03 mm. to ‘075mm. The walls are thick (about *004— 
‘007 mm.) and straight or only slightly curved. The end walls are frequently 
thicker than the others. There is usually a dark round or oval mark in the 
centre of each cell, presumably a papilla (see Pl. 87. fig. 2), which is some- 
times slightly elongated into a short ridge. 
