2 87 
the Periderm of Fossil Lycopodiales . 
The Species examined. 
The present paper is based on an investigation of the material in the 
collections at University College, London, and, by kind permission of 
Dr. A. Smith Woodward, of that in the Williamson Collection at the 
Natural History Museum. All the forms are British with the exception of 
Sigillaria spinulosa , which comes from Autun. 
The following species showing a development of periderm have been 
examined : 
Lepidodendron selaginoides ( vasculare ) Sigillaria scutellata 
„ Harcourtii 
„ Hickii 
,, brevifolium ( Veltheimianuin) 
„ intermedium 
„ obovatum 1 
L. (L epidophloios) Wunschianum 
„ fidiginosum 
„ Scottii 
Lepidodendron sp. 
L epidophloios sp. 
reniformis 
organum 
elegans 
„ tesselata 
„ sp. ( Eusigillariae ) 
„ spinulosa 
Botlirodendron mundum 
Stigmaria ficoides 
,, of Botlirodendron 
„ sp. 
The specimens examined of Lepidodendron acute at um , parvulum , and 
macrophyllum 2 show no periderm. 
The Phellogen. 
(i) Place of Origin. 
In all cases periderm formation originates in the outer cortex, from 
a zone of cells which may be situated 
(a) almost immediately within the leaf-bases, with one to seven or so 
layers of primary cortex outside, as in 
Lepidodendron selaginoides 
„ brevifolium 
„ intermedium 
„ obovatum 
„ Wunschianum 
L epidophloios sp. 
All the ribbed Sigillariae 
or ( b ) deeper in the outer cortex (about fifteen to thirty layers), as in 
Lepidodendron fidiginosum 
„ Scottii 
„ Harcourtii 
„ Hickii 
L epidophloios sp. 
Stigmariae. 
1 This species is not considered by Zalessky to be the true L. obovatum , Sternberg. 
2 The specimen shown in Text-fig. i, b, may possibly be L. macrophyllum. 
