164 FOSSIL PLANTS. 



Phytolithus parmatus. 



Steinhauer (in part), Trans. Amer. Phil. Soc. vol. i. 2nd. ser. p. 287, 

 pi. vii. fig. 1, 1818. 



Vegetable Impression. 

 Allan, Trans. Koy. Soc. Edinb. vol. ix. p. 235, pi. xiv. 1823. 



Shuppenpflanzen. 



Rhode, Beitr. z. Pflanz. d. Vorwelt. p. 16, pi. iii. figs. 1-8. 



Remarks. Several species of Ulodendron are united here. 



Many palseobotanists have already adopted the view that the genus 

 Ulodendron is only a condition of Lepidodendron. In this I so far agree, but 

 though several species of Ulodendron belong to Lepidodendron, there are 

 other named species of Ulodendron, which in the form and arrangement of 

 their leaf-scars agree entirely with the Clathrarian-Sigillariae. Hence certain 

 of these so-called Ulodendron have been placed by me in Sigillaria. This 

 latter view is not the opinion generally accepted, but I have come to this 

 conclusion after an examination of many beautifully preserved specimens. 

 Almost all the misconceptions on the true affinities of Ulodendron have arisen 

 through the neglect of a very essential element for the right understanding 

 of these fossils, and one which only requires to be mentioned to be accepted 

 by all botanists, viz., that only well-preserved examples should be taken 

 into consideration when critically considering the affinities of this genus ; 

 unfortunately this has not always been done. 



When determining the various species of the genera Lepidodendron and 

 Sigillaria, unless the outer surface of the bark is well preserved and exhibits 

 the form and arrangement of the leaf-scars, it is admitted that the plants do 

 not show the characters by which a specific, or even in some cases, a generic 

 determination can be made. In Ulodendron, on the other hand, though it is 

 difficult to account for it, decorticated and badly-preserved specimens, if only 

 they show the characteristic scar of the genus, have often been regarded as 

 in a sufficiently good state of preservation, not only for generic identification, 

 but even for the creation of new species, notwithstanding that the close 

 affinity of Ulodendron and Lepidodendron, both in regard to their internal 

 structure and general characters, is fully recognised. 



The form and size of the large scars have commonly been made the 

 character on which the various species of Ulodendron have been founded 

 the description generally mentioning as the chief distinguishing point " scar 

 so long by so broad." Such arbitrary specific distinctions to be of any 

 value must infer that the plant sprang into existence with the large 

 Ulodendroid-scars fully developed ; this view of course was never intended 

 by the authors who described the various species, characterised as indicated 

 above ; but to make the species of true value, an inference of this nature is 

 quite legitimate. 



Now it is obvious that the Ulodendroid-scars when they first appeared 

 were very small, and this I have proved to be the case by observation, having 

 traced them through their different stages of growth on stems of Lepido- 

 dendron Veltheimianum, Sternb., where the leaf-scars were well preserved. 

 Or, on stems having leaf-scars similar in all respects to those of Lepidodendron 

 Veltheimianum, Sternb., and of which, had portions of the stems been broken 

 off, either from between or from the sides of the scars, could not have been 

 by any character distinguished from specimens of that plant. 



On a specimen of Sigillaria (Ulodendron) Taylori, Carr., to be referred to 

 again, I have observed the appendicular organs attached, when only about 

 three-quarters of an inch in length, and the branch bearing them must have 

 been of considerable breadth, for though its full breadth, as shown on the 

 specimen, is only about 3 inches, still it has probably been a little broader. 

 The earliest stage of the Ulodendron-scars of Lepidodendron Veltheimianum 

 with which I am acquainted, is shown on a specimen 22 inches long and fully 



