434 PALAEONTOLOGY OF ILLINOIS. 



GENUS ULODENDRON, Rhode. 



Beitr., PI. 3, fig. 1, Endl. Gen., p. 70. 



STEM arborescent, simple, ? covered with rhomboidal cica- 

 trices, remains of deciduous, strobile-like branches, densely 

 covered with imbricate leaves. 



This description, translated from Unger's Genera, p. 262, does not give a 

 clear idea of the form and nature of the trees referable to this genus, for the 

 good reason that now, after years of research among the remains of fossil plants, 

 these species are known to us by mere detached fragments, whose relation is 

 uncertain. Prof. Brongniart has considered this genus as merely representing 

 species of Lepidodendron, and this opinion has been more or less generally ad- 

 mitted by others. And truly, the bark of the trees or of the species referred 

 lo this genus, bear cicatrices or bolsters generally of the same type as those of 

 the true Lepidodendron, with also the leaf scars and vascular points of the same 

 kind and placed in the same position. 



They differ essentially in this : that they have two or more parallel rows of 

 large round or oval scars, which appear as if they had been made by the base 

 of large strobiles or cones, thickly covered with scales or short leaves. These 

 organs have not yet been found in connection with trunks or branches, and 

 therefore their origin is hypothetical. They have been considered either as the 

 cicatrices of a peculiar kind of leaves, a supposition which is not admissible, or 

 as the scars of lateral abortive or adventive branches, a supposition "also unsus- 

 tainable for vegetables regularly dichotomous, like those of the genus Lepido- 

 dendron, or as the scars of large strobiles like those of our Lepido&trobus prin- 

 ceps, (this Report, vol. ii, pi. 45, fig. 1) whose size corresponds with that of 

 the cicatrices, and prevents the idea that they may be borne at the top of the 

 slender branches of Lepidodendron. 



I consider this last supposition as the right one. These scars, one or two 

 inches in diameter, are placed in parallel rows, alternate or opposite to each 

 other, at a distance varying vertically from two to eight inches. It is possible 

 that these organs]were borne on peculiar fruit-bearing branches of species of Le- 

 pidodendron. The horizontal distance between them is not great : 2 to 3 inches. 

 What seems also to indicate branches is the small size of the cicatrices of the 

 bark, which in all our specimens is about the same. There is, nevertheless, a 

 peculiar character remarked on the specimens of all our American species, 

 which is not observable on the bark of species of Lepidodendron. Their sur- 

 face is ribbed lengthwise by irregular ridges, from one-fourth to one-half of an 

 inch broad, one to two lines thick, generally angular at the top, bearing be- 



