92 EXPLAIN ATION OF PLATE 56. 



size. On comparing this scar with those upon the 

 bark of Fig. 2, it may be seen that the different 

 modes of articulation of the leaves with the cortical 

 integument present obvious characters, on which 

 specific distinctions may perhaps most easily be 

 established, in this very obscure and curious family 

 of extinct plants. See various figures of these leaf- 

 scars in Lindley and Hutton's Fossil Flora, Plates 

 55. 56, 57. 71. 72. &c. In Figs. 2, and 2', as in 

 many other species, decurrent lines are visible on 

 both sides of the scar. (Original.) 

 Fig. 3. Ulodendron Allanii, (nobis) scale one-fifth. 

 See V. I. p. 475. Note. Drawn from a plaster cast 

 of an impression on sandstone, in the Museum of 

 the Royal Society of Edinburgh from the Coal for- 

 mation at Craigleith. This sandstone has formed 

 a natural mould on the outer surface of a stem, 

 which has entirely perished ; our cast gives a fac- 

 simile of the small rhomboidal scales, and of three 

 large round scars on the exterior of the trunk. 

 This impression has been figured, in an inverted 

 position, by Mr. Allan in Vol. IX. Trans. Royal 

 Soc. Edin. 1823. PI. XIV. p. 236. (Original.) 



Our figure represents the trunk in its natural 

 position. In the centre of each scar is a cavity, 

 indicating the place of attachment of a cone. The 

 upper portion of each scar is marked with furrows, 

 produced by pressure of the long radiating scales 

 at the bottom of the cone. This pressure has 

 nearly obliterated the smaller rhomboidal scales of 

 the bark, in those parts where the furrows are 

 deepest; on the lower portion of the scars, the 

 scales of the bark have been but slightly modified 

 by pressure of the cone. 



