XC PROCEEDINGS OF THE GEOLOGUCAX SOCIETY. [vol. lxxix, 



8 inches; from a creeping rhizome were given off: slender cylin- 

 drical green shoots superficially similar to the leaves of the recent 

 pillwort, but differing in their occasional, regular dichotomy and in 

 the small cylindrical sporangia at the tips of some of the ultimate 

 branchlets. The spores were adapted to dispersal on land. In the 

 creeping stem and the aerial branches was an axial strand of con- 

 ducting tissue. Simple hairs on the rhizome absorbed material 

 from the peaty soil, and sparsely-scattered stomata on the green 

 erect stems regulated the gaseous exchange between the plant and 

 the surrounding air. 



Hornea, although rather smaller, resembled Hhynia in habit ; 

 but its subterranean stem was a tumid, irregularly-lobed organ, 

 and the terminal sporangia closely resembled the capsules of recent 

 species of Sphagnum (the bog-moss), the spores being confined to 

 a region between the wall and a central column of sterile tissue. 



Asteroxylon was distinguished from the other two genera by 

 the presence of crowded scale-like leaves on the aerial shoots, a 

 slightly more elaborate conducting strand, and by other characters. 

 Asteroxylon was clearly a land-plant ; like JRhynia it had stomata, 

 whereas the apparent absence of stomata in Hornea may mean 

 that it was more aquatic than terrestrial. Associated with the 

 steins of Asteroxylon were leafless axes and with them detached 

 sporangia : there is good reason to believe that the leafless forked 

 branchlets were originally prolongations of the leafy aerial stems, 

 and that they bore the sporangia. 



These genera raise many interesting botanical problems ; but 

 I will confine myself to a brief consideration of the probable 

 position of the Khynie plants in relation to existing types and to 

 other Devonian fossils. The three genera are included by Kidston 

 and Lang in a group — Psilophytales, so named from the genus 

 Psilophyton, described long ago from the Devonian of Canada and 

 recorded from several other regions. In the recent genus Psilotum, 

 a widespread Southern Hemisphere member of the group to which 

 our Club Mosses (species of Lycopocliuni) belong, we have a rootless 

 and practically leafless plant similar in general habit to Rhynia 

 and Hornea, but differing in the structure of the sporangia and in 

 their relation to the rest of the plant-body, as also in some other 

 featui*es. In its leafy shoots, and in the structure of the con- 

 ducting tissue, Asteroxylon presents a closer resemblance to some 

 species of Lycopocliuni ; but its sporangia are more fern-like. 



Before giving further thought to the Bhynie plants, we will 



