part 2] ANNIVERSARY ADDRESS OF THE PRESIDENT. XCV 



The broader spinous stems first described by Sir William Dawson 

 from the Lower Devonian of Graspe as Arthrostigma gracile, 

 recorded by Dr. R. Kidston from beds of similar age in Perthshire, 

 and more recently by Dr. T. Gr. Halle from the Lower Devonian 

 flora of Roragen and from China, clearly belong to a plant which, 

 if not generically identical with Psilophyton, is nearly allied to it. 

 A relatively slender vascular axis occupied the centre of the stem, 

 and on the surface were spine-like leaves or emergences, arranged 

 either spirally or in whorls. Occasional lateral branches were given 

 off at a wide angle, and then bent abruptly upwards parallel to the 

 main axis, a habit analogous to that of some succulent Euphorbias, 

 plants which in some other respects recall the Devonian genus. 

 Specimens apparently of the same generic type as Arthrostigma 

 have been described from the Middle Devonian of Bohemia ; but 

 the genus is characteristic of the earliest Devonian floras. 



Reference has already been made to the occurrence in both 

 Lower and Middle Devonian beds of dichotomously-branched 

 slender axes similar to those described from Bohemia as species of 

 Hostimella. A characteristic feature of these fossils is the occur- 

 rence of a bud-like structure close to the point of bifurcation : it 

 has been suggested that this is actually an aborted bud ; and in 

 this connexion it may be noted that other slender axes from beds 

 of the same age, but with a different disposition of lateral branches, 

 frequently bear more than one branch at the same point on the 

 major axis. The type to which I refer resembles some of the 

 specimens referred by Nathorst to the genus Apliyllopteris, and 

 similar fossils are included in Zoster opliyllum. These various forms 

 of branched axes cannot be assigned with any degree of confi- 

 dence to a systematic position : the Hostimella type resembles 

 the lateral branch-systems of Psilophyton goldschmidti ; while 

 that of the Apliyllopteris type may be compared with specimens 

 from Middle Devonian rocks in Germany described, on good 

 grounds by Solms-Laubach as portions of a large Fern-frond 

 without leaflets, and with undoubted fern raches from Upper 

 Devonian rocks. 



The comparatively-large branched axis, described by J. W. 

 Salter from Devonian beds at Thurso as Gaulopteris peacliii, 

 differs from any of the older Devonian Psilophytales, and bears a 

 close resemblance to the stems of certain Ferns and to those of 



