CARBONIFEROUS LYCOPODS AND SPHENOPHYLLS. 4? 



ever, an important character of this species is the presence of 

 well-defined irregular transverse ridges which extend over the 

 whole area of the leaf-cushion, which also does not appear to 

 be keeled. (Fig. 6.) 



In the great majority of Lepidodendra the bark and leaf- 

 cushions keep pace in growth with the increase in diameter of the 

 stem, but in Lepidodendron Veltheimianum, Sternb., and a few 

 other Carboniferous Lycopods, 1 although the leaf-cushions and 

 bark increase in size with age, as in other species, to a certain 

 extent, the bark becomes longitudinally fissured from the 

 increase in the girth of the stem. These fissures in casts 

 of the specimens necessarily appear as elevated, more or less 

 irregular, ridges. Pressure often flattens these ridges, which 

 then extend over neighbouring portions of the bark and entirely 

 obliterate the leaf-cushions, and such specimens of Lepidodendron 

 Veltheimianum have frequently been mistaken for Sigillaria. 

 This condition is only seen in aged specimens, 2 some of which are 

 figured by Schimper. 3 I believe the Lyginodendron Landsburgii 

 of Gourlay is founded on an extreme, though similar, condition of 

 an old Lepidodendron stem with which the Lyginodendron 

 of Williamson has no affinity. 4 



The fructification is in the form of cones. In the great 

 majority of the species these terminate the small branches as in 

 Lepidodendron ophiurus, Brongt. (No. 912), and Lepidodendron 

 lycopodioides, Sternb. (No. 2232). In a few species, as Lepido- 

 dendron Veltheimianum, Sternb., and Lepidodendron Landsburgii, 

 Kidston. the cones are sessile, and are borne on the large stems 

 in two opposite rows, the cones in one row alternating with those 

 of the other row. It is a most peculiar and marked character of 

 the so-called Ulodendroid Lycopods that the fructification is only 

 produced on stems of considerable size and age. 



A stem of Lepidodendron Veltheimianum, Sternb., in my pos- 

 session, about, 4 inches wide, shows the point to which the cones 



1 Sigillaria discophora, Konig sp., is another example. 



2 I possess several specimens of Lep. Veltheimianum showing various 

 states of this condition. — See Nos. 62, 62a, and 76. 



3 Schimper — (Koechlin-Schlumber and Schimper), Lt terr d. Transition 

 de Vosges, PI. XXIII., 1S62. 



4 Gourlay, Description of Lyginodendron Landsburgii, Proc. PhiL Soc* 

 of Glasgow, Vol. I., Part II., p. 108, 1841-44. 



