206 /- EPIDODENDKEA E. 



named Ulodendron since Sternberg's time. Their distinguishing feature is 

 the presence on their outer surface, which is covered with ^epidodendron- 

 cushions, of two opposite vertical rows of enormous usually depressed 

 platter-shaped or cup-shaped scars, which may be either crowded together 

 till they touch one another, or be separated by wider intervals within each 

 row. The Ulodendron-character is usually seen in strong thick stems, in 

 which branching is an extremely rare occurrence ; but Williamson l has 

 described one case of the kind, in which one of the large cup-shaped scars 

 lies exactly in the angle between the members of the dichotomy. It is not 

 often that these stems are found with the surface-characters clearly shown ; 

 they are usually observed in the form of interior casts, on which the 

 position of the leaves is shown by the small linear protuberances due to 

 the trace-bundles. The Ulodendrae have recently been submitted to 

 careful examination by Stur 2 , Kidston 3 , and Zeiller 4 . In Kidston will be 

 also found a very complete collection of the older literature. The authors 

 just cited, though differing in their views on other points, all agree in 

 thinking that the stems in question show variations in the character of their 

 surface, and may accordingly be divided into three groups. We will 

 confine our attention for the present to the first of these groups, which 

 shows an almost absolute agreement with the normal and well-known 

 Lepidodendron Veltheimianum, while the remains contained in it are 

 usually named Ulodendron commutatum, Schpr., and are directly united 

 with that species by the authors just mentioned 5 . The leaf-cushions in 

 specimens of Ulodendron are however as a rule considerably smaller than 

 those of ordinary Lepidodendron-stems of equal thickness, though they 

 agree with them in other respects. If we examine the peculiar platter- 

 shaped or cup-shaped scars, we find that they are roundish, elliptic or 

 ovate, and more or less deeply depressed, and that they appear therefore 

 on the mould as a convex projection ; a somewhat sharp edge forms their 

 boundary line. At the deepest point is a nearly circular scar of separation, 

 in the middle of which a dot-like trace may still be seen when the state of 

 preservation is sufficiently good. This point of separation is not however 

 central ; it can always be seen, more or less distinctly, to be pushed 

 towards the lower side of the cup, so that the slope on that side is steeper 

 and the radii shorter than on the upper side. The whole surface of the 

 slope surrounding the scar bears small keel-like protuberances arranged 

 pretty nearly in radiating rows, which look like the leaf-trace-marks of 

 poor interior casts of Lepidodendrae, and are apt to run together into 

 irregular and indistinct radial ribs, especially on the upper flatter slope of 

 the platter. These stripes may be the only markings visible on the entire 



1 Williamson (1), x, p. 499. Stur (5). * Kidston (2). * Zeiller (3) and (11). 



5 Schimper (1), t. 63; Kidston (2), t. 3 ; Brongniart (1), vol. ii, t. 18; Stur (5\ tt. 21, 22, f. 3. 



