. 



pre-carboniperous plants. 

 Genus Psilophyton.— Dn. 



37 



48. PSTLOPHYTON PRINCEPS, Dn— (PI. IX. PI. X, Figs. Ill to 119. PI. 

 XI, Figs. 127 to 129, & 133 & 134.)— J. G. S., XV, 479; Fig. 1. 

 Ibid. XVIII, 315. Ibid. XIX,, 46.— L. D., M.D., Gasp<5; also 

 Upper Silurian. 



Sterna branching dicfwtomomly, and covered with interrupted ridget. 

 Leaves rudimentary, or short, rigid and pointed; in barren stems, 

 numerous and spirally arranged ; in fertile stems and branchlets 

 sparselg scattered or absent; in decorticated specimens repre- 

 sented by minute punctate scars. Young branches circinate; 

 rhizomata cylindrical, covered with hairs or ramenta, and having 

 circular areoles irregularly disposed, giving origin to slender 

 cylindrical rootlets. Internal structure — an axis of sealariform 

 vessels, surrounded by a cylinder of parenchymatous cells, and 

 by an outer cylinder of elongated woody cells. Fructification 

 consisting of naked oval spore-cases, borne usually in pairs on 

 slender curved pedicels, either lateral or terminal. 



This species was fully described by me in the papers above cited, from 

 Bpecimens obtained from the rich exposures at Gasp^ Bay, and which 

 enabled me to illustrate its parts more fully perhaps than those of any 

 other species of so great antiquity. In the specimens I had obtained, I 

 was able to recognize the forms of the rhizomata, stems, branches and rudi- 

 mentary leaves, and also the internal structure of the stems and rhizo- 

 mata, and to illustrate the remarkable resemblance of the forms and struc- 

 tures to those of the modern Pailotum. With the fructification I was less 

 successful. The only specimen which I could regard as showing the fruit, 

 appeared to me to present an assemblage of sessile scales. A large number 

 of more perfect specimens obtained last summer enable mo now to state 

 that the supposed scales are really narrowly ovate sporangia ; and 

 that when mature they were borne, usually in pairs, on curved and appa- 

 rently rigid petioles, in the manner represented in Figs. 102 to 108. 

 Under the microscope these sporangia show indications of cellular 

 structure, and appear to have been membranous in character. In some 

 specimens dehiscence appears to have taken place by a slit in one side, and 

 clay having entered into the interior, both walls of the spore-case can be seen. 

 (Fig. 108.) In other instances, being flattened, they might be mistaken 

 for scales. No spores could be observed in any of the specimens, though 

 in some the surface was marked by slight rounded prominences, possibly 

 the impressions of the spores within. This peculiar and very simple style 



r. . 



