140 LYCOPODIALES [CH- 



with comparatively thick walls enclosing meshes filled with 

 large-celled parenchyma. It is worthy of note that if such a 

 branch were exposed to decay, the earlier destruction of the 

 more delicate tissue in the meshes of the secondary cortex 

 would produce a series of oval depressions, corresponding to 

 the parenchymatous areas, separated by a projecting reticulum 

 of the more resistant elements : a cast of this partially decayed 

 surface would be indistinguishable from that of some types 

 of Sigillaria or of a Lyginodendron. The inner regions of 

 the cortex of the type-specimens have not been preserved. 

 The xylem, which is the only part of the stele represented, 

 has the form of a protostele or solid cylinder of scalariform 

 tracheids with peripheral groups of narrower protoxylem ele- 

 ments which mark the points of exit of the leaf-traces : in a 

 branch 1 — 2 cm. wide the xylem column has a diameter of 

 3 mm. The small leaves (fig. 143, B, C), similar to those of a 

 Sigillaria, are sub-rhomboidal in section near the base and 

 approximately circular near the apex'. The mesophyll consists 

 of palisade cells having the appearance of typical chlorophyll- 

 tissue. The heterosporous strobili attributed to this species bore 

 microsporangia on the upper and megasporangia on the lower 

 sporophylls ; the megaspores, of which a considerable number 

 occur in each megasporangium, are identical in size with those 

 of another Culm form, Lepidodendron rhodumnense. Some of 

 these have retained traces of prothallus tissue, and iu jne spore 

 Renault figures what he regards as an archegonium : the 

 drawing is by no means convincing. 



2. Lepidodendron rhodumnense, Renault''. 



The species from the Culm of Combres (Loire) agrees in its 

 solid xylem cylinder and in the differentiation of the secondary 

 cortex, as also in the association of two kinds of spore, with 

 Lepidodendron esnostense. A comparison of the leaves of the 

 two types reveals certain differences which may be of specific 

 rank, but, apart fi-om minor differences, these Culm species 

 may be classed under one anatomical type. 



' For description of the leaf-anatomy, see pp. 98, 99. 

 2 Renault (79) p. 249, PL x. 



