the Periderm of Fossil Lycopodiales . 
307 
ference in a tissue which attained a great thickness (7 or 8 cm.), and the 
growth of which may have been very rapid. 
(d) Turning to the irregular wide-celled forms of Stigmarian periderm, 
it is found from tangential sections that here also a large number of the 
wide outer cells are chambered. 1 Text-fig. 20, A, is drawn from a tangential 
section of the specimen figured in transverse section in Text-fig. 20, B, and 
it is seen that many of the cells show subdivisions. 
B 
V 
Text-fig. 20. Stigmaria sp. (type 2). A, tangential section in the outer part of the periderm 
showing chambered cells. Will. Coll., 1785. B, transverse section of the same specimen; the 
probable position of the phellogen is shown at p . Will. Coll., 1780. x 55. 
In other cases, where more narrow files intermix with the distended 
ones and the wide cells which become chambered occur in irregularly lenti- 
cular areas, a somewhat Dictyoxylon-like appearance is produced in tan- 
gential section (Text-fig. 21). As has been mentioned, Williamson described 
a series of sections of the above type, thinking they were identical with 
Renault’s Sigillaria spinulosa . 2 From this series, in which there is a large 
quantity of the regular inner portion of the periderm preserved, it is seen 
that the dividing cells occur in the outer wide-celled portion of the secondary 
tissue, and die out rapidly in the regular inner part. 
It is probable that these Stigmariae should be referred to stems which 
have similar heterogeneous periderms. 3 
1 First noticed by Williamson (43), p. 20, Figs. 24 and 49. 
2 Williamson (39), pp. 353-6, PI. XXV. 
3 As already found in Glathraria and Stigmaria Brardi , Renault ( 21 ), p. 194. 
