56 THOMAS HICK, B.A., B.SC, A.L.S. 



from an average of 2 mm. (^ in.), while the elliptical ones are some- 

 what larger, and measure for the most part 2*1 mm. ( T Vin.) by 

 1-9 mm. (^ in.). It is obvious, therefore, that the objects to be dealt 

 with are small, but there is nothing to show that they are in an 

 immature state. In most of them one recognises without difficulty 

 (Fig. 1) a central cylinder or stele, surrounded by a cortex, and a peri- 

 pheral or epidermal layer. The stele, when single, is circular in 

 transverse section, with a diameter varying between - 4 and 075 mm. 

 (0^- and y^g-in.). In many cases, however, it is preparing for, or in a 

 state of, division, and is then more or less elliptical, measuring 1 by 

 08 mm. (^-g- by -£$ in.). The cortex, including the epidermis, varies in 

 thickness from 0*4 to 0-8 mm. (-^ to ^ in.). 



The Epidermis. 



The peripheral layer or epidermis is not usually quite distinct, but 

 when it is, as in No. 115, 1 it presents itself as a single layer of cells. 

 No signs of stomata have yet been seen in it. In some sections, such 

 as the one just referred to, it is provided with a covering of multi- 

 cellular hairs, the density of which varies in different specimens, while 

 in some no hairs are visible. In these last, however, it is not certain 

 that the outermost layer is actually the epidermis. For the most 

 part the hairs are seen only in transverse section. They are very 

 rarely, and then for short lengths only, presented in longitudinal 

 section. As in the epidermal cells, no cell contents have as yet been 

 met with in the hairs. 



Putting together the details observable in various fragments, the 

 hairs may be described as filaments made up of a single row of cells 

 placed end to end. At the base, what appears to be a sort of pedestal 

 is sometimes seen, but no indications of anything of the nature of a 

 terminal gland have been found. From the fact that transverse 

 sections of the stem show the hairs, when present, also cut, for the 

 most part, transversely, it seems probable that the latter were 

 appressed rather than spreading. 



1 Here and throughout the figures refer to the Register of the "Cash" 

 Collection of sections of Carboniferous Plants in the Manchester Museum, 

 Owens College. 



