48 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



had been attached as mamilla>like elevations. 1 This must indi- 

 cate that the cone when removed was in a very early state of 

 development, for the cup-like depressions are formed by the base 

 of the sessile cone pressing against the bark which grows up 

 round it. These cups participate in the increase of the stem, and 

 long after the fall of the cone continue to increase in size, and 

 thus is formed the characteristic cup-like depressions on the 

 bark, which gave rise to the genus Ulodendron, L. and H. 2 In 

 the Ulodendroid scars of Lepidodendron the scar of the cone 

 attachment — the umbilicus — is approximately central. 



But this mode of fructification is not restricted to Lepido- 

 dendron, for it also occurs in Sigillaria and Boihvodendron. 



The cones are heterosporons, the lower tracts bearing the 

 macrosporangia and the upper the microsporangia. There is, of 

 course, the possibility of some Lepidodendra having had homo- 

 sporous cones, but there is no clear evidence that this was the 

 case. The detailed structure of the cones will be described under 

 the genus Lepidostrobus, Brongt., for, unfortunately, in the 

 majority of cases, the cones are found separated from their stems, 

 and it is then frequently impossible to refer them to their parent 

 species. This circumstance has necessitated the formation of 

 the genus Lepidostrobus, Brongt., for their reception. 



When the epidermal layer of the bark is removed, the exposed 

 surface is irregularly striated longitudinally and only shows the 

 cicatrice of the foliar bundle. The genus Aspidiaria, Presl, is 

 in part founded on such specimens of Lepidodendron.' 3 



The leaves of Lepidodendron are entire and single-nerved. On 

 Lepidodendron lycopodioides, Sternb., Lepidodendron ophiurus, 

 Brongt., and many other species, they are lanceolate. On Lepido- 

 dendron longifolium, Brongt., and Lepidodendron obovatum, 

 Sternb., they are very long and grass-like— on the larger stems of 

 the latter species attaining a length of 30 inches. 4 The leaves 

 must have remained on the branches a long time, increasing in 

 size with age. This is clearly seen on specimens on which the 



1 See Kidston, Ann. and Mag. Nat. Hist., Ser. 5, Vol. XVI., PI. IV., 

 Fig. 2, 1885. 



2 Lindley and Hutton, Fossil Flora, Vol. I., p. 22, 1S3L 



3 Presl, in Sternberg, Vers. II., p. 180, 1838. 



Zeiller, Flore fons. Bassin houil de Valenciennes, p. 442. 



