305 
the Periderm of Fossil Lycopodiales. 
In Sig ill aria scutellata it has been noted that some of the cells, 
especially in the deeper portions of the phelloderm, are chambered, 1 
but no vertical sections of this species have been examined in the present 
investigation. 
(e) It would appear that the complex periderm known as ‘ Dictyoxylon 
cortex ’ may be regarded as derived on similar lines to the above types. 
Dictyoxylon cortex, as often described, consists essentially of a network, 
Text-fig. 17. Tangential section in the 
periderm of Sigillaria sp., showing ver- 
tical groups of chambered cells. Will. 
Coll., 662. x 100. 
Text-fig. 18. Sigillaria spinulosa. Transverse 
section in the periderm showing the origin of the thin- 
walled meshes, «, in the cells of the regular radial 
files, b. Will. Coll., 665. x 100. 
of which the strands are ordinary periderm cells, while the meshes, visible 
alike in transverse and vertical sections, are filled with thin-walled, brick- 
like parenchyma. 2 It is not to be confounded with the primary outer cortex 
of Lyginodendron and Heterangmm with its strands of fibrous sclerenchyma, 
to which the term c Dictyoxylon * is also applied. 
According to Renault, the meshes in Sigillaria spinulosa , &c., are not 
found in the inner part of the tissue, and gradually increase in size towards 
the periphery. From the transverse section shown in Text-fig. 18, it will 
1 Arber and Thomas (1), p. 142. 
2 Described in the following : Lepidodendron rhodumnense , Lepidodendron esnostense , Sigillaria 
spinulosa , Sigillaria lepidodendrifolia } Stigmaria Brardi. 
