CARBONIFEROUS LYCOPODS AND SPHENOPHYLLS. 41 



parichnos. Leaves simple, entire, single-nerved, lanceolate, short, 

 or long and grass-like. Fructification in the form of cones 

 (Lepidostrobus), the lower bracts of which bear macrosporangia 

 and the upper microsporangia. The cones are borne at the 

 termination of the branches, or sessile and placed in two opposite 

 vertical rows — (Ulodendron in part). In the sub-cortical con- 

 dition the trunk is irregularly striated longitudinally and the 

 leaf cicatrice is single (the vascular bundle cicatrice). 



Interned structure of stem. — As Lepidodendron vasculare, 

 Binney, sp. ( = Lepidodendron selaginoides, Carruthers and 

 Williamson) 1 is the species most commonly met with showing its 

 internal organisation, it may be conveniently taken in illustrating 

 the anatomy of Lepidodendron. 



In a young stem the central axile bundle consists of irregularly 

 disposed tracheides, of which the outer and much smaller are 

 mostly spiral, and the inner and larger scalariform. The centre 

 of the bundle is composed of isodiametric spiral tracheides mixed 

 with parenchyma. 



The primary bundle is surrounded by a zone of delicate small- 

 celled parenchyma — the inner cortex of Williamson. 



Succeeding the inner cortex is a zone of large-celled but very 

 delicate parenchyma — the middle vortex of the same author. 

 This is enclosed by a zone of large thick-walled parenchyma 

 which forms the ground tissue of the leaf-cushions. 2 



1 1862, Sigillaria vasculare, Binney, Quart. Journ. Geol. Soc.,Yo\. XVIII., 

 p. 106, PI. IV.; 1869, Lepidodendron selaginoides, Carruthers, Monthly Mic. 

 Journ., Octr., p. 177, PI. XXVII. It is quite possible that the stems here 

 described may really belong to Lepidodendron selaginoides, Sternberg, 

 [Essaiflore mondeprim,, fasc. II., p. 29, PI. XVI., fig. 3, PL XVIII., fig. 1.) 

 which only represents the smaller branches of Lep. lycopodioides, Sternberg, 

 ibid., fasc. II., p. 29, PI. XVI,, figs. 1, 2, and 4), as that species is common 

 in the Lower Coal Measures, the horizon in which the stems showing struc- 

 ture are found. ( This probability is further heightened by the fact that 

 the imperfectly preserved leaf-cushions on specimens showing structure 

 when removed from the matrix have very much the form of those of that 

 species. As, however, its identification is by no means certain, it is much 

 better to use Binney' s name of vascidare for these specimens. 



2 See also Bower, "On the Structure of the Axis of Lepidostrobus 

 Broimii, Schimper, Ann. of Bot., Vol. VII., No. 27, Sep., 1893, pp. 343, 

 344. 



D 



