92 EXPLANATION OF PLATE 50. 



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 es- 

 tablished, 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. 356. Note. Drawn from a plaster cast of an 

 impression on sandstone, in the Museum of the Royal 

 Society of Edinburgh from the Coal formation at 

 Cragleith. 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. 



