Notes. 
793 
quoted memoir 1 the authors draw attention to a section in which the 
outer layer appeared two cells in thickness, and which ‘ suggested that 
we have here a peridermic formation * even although the cells lacked 
the clear definition of a well-developed periderm. 
The object of this note is to place on record what appears to be an 
undoubted peridermic formation in roots from the lower coal-measures 
of England, which also show a highly specialized ‘ epidermoidal layer/ 
The slides from which the present descriptions and sketches have been 
taken are S. 4014 and 4015, from the series S. 4013-7, continued in 
S. 3556-8, in the general collection of the geological department of 
the British Museum (Nat. Hist.). 
The root appears to have had a diameter of about 15 mm., but it is 
impossible to be quite accurate as the pith is not well preserved, and 
the stele is somewhat compressed and split by stigmarian rootlets. 
The preservation of the inner and middle cortex is poor, but there is 
sufficient evidence of continuity between these layers and the outer 
cortex, which is crushed against the well-preserved ‘ epidermoidal layer/ 
continuous round the root, see Fig. 30. 
The individual epidermoidal cells are very large, ranging from -175 
to -2 mm. in diameter, and considerably exceeding any other tissue in 
the root. The outer membrane of each cell is thick, and from it 
fibrous fragments project into the cell-cavity, Fig. 31 ; it is not possible 
to ascertain the minute structure of these fibres, and I am not aware 
of any similar appearance in recent plants that would throw light on 
their nature. 
x 100. 
Fig. 31. 
The epidermoidal cells appear to originate as the enlarged outer 
layer of the periderm, see Fig. 32 A and B, and it seems probable that 
they took the outermost position with some irregularity, as in most 
cases the linear arrangement of the periderm cells has been disturbed, 
1 Will, and Scott, loc. cit. , Pl. XVII, Fig. 11, and p. 694. 
