i66 



STUDIES IN FOSSIL BOTANY 



Fig. 67). 



The characteristic feature of the Ulodendron 

 stem consists in the presence 

 of roundish scars, often of very 

 large size, usually arranged 

 alternately in two vertical 

 rows, one row on each side 

 of the stem. On the larger 

 Ulodendra these scars have 

 a diameter of from 4 to 6 

 inches. Within the scar, 

 usually somewhat below the 

 centre, is a print or stump, 

 representing either the stalk 

 or the woody cylinder of 

 some lateral appendage. The 

 scar as a whole is depressed, 

 having the form of a shallow 

 cup, with the print or umbili- 

 cus at the bottom (see Fig. 

 67). The surface of the cup 

 is usually marked with radiat- 

 ing ridges on the part above 

 the umbilicus, while the lower 

 Surface of P art bears spirally arranged 



Fig. 67. — Ulodendron. 



branch, showing two large scars, with prominent DOintS 



the central print c, and numerous 



Lepidodendroid leaf-bases. On the 



right the leaves are seen. Reduced. 



After Schimper. The large scars are 



really depressions, but, owing to the 



shading, appear in the figure as 



elevations. They can be seen as 



depressions if the figure is reversed. 



The nature of these 

 curious objects was long in 

 dispute, and is still by no 

 means cleared up, though 

 specimens have been de- 

 scribed with " cones " still attached to the scars, 1 thus 



1 D'Arcy Thompson, "Notes on Ulodendron and Halonia" Trans. 



