16 T. G. HALLE, LOWER DEVONIAN PLANTS FROM RÖRAGEN IN NORWAY. 



In the next following publications of Dawson (especially those of 1862 and 1863) 

 very little of any interest is added to our knowledge of Psilophyton princeps with the 

 exception of the description of the petrified specimen just mentioned. 



In his comprehensive report on »The fossil plants of the Devonian and Upper 

 Silurian formations of Canada» (1871), Dawson gives further contributions to the know- 

 ledge of Psilophyton princeps, especially as regards the fructification. Instead of the 

 obscure object shown in fig. 1 e, p. 479, in the paper of 1859, remains of a very different 

 kind are now described as the fructification of this species. In the following passage in 

 the diagnose, their chief characters are thus expressed: »Fructification consisting of 

 naked oval spore-cases, borne usually in pairs on slender curved pedicels, either lateral 

 or terminal». This supposed fructification will be further considered below under the 

 name of Daivsonites arcuatns. Without entering here into any discussion of this subject, 

 it will suffice to state that, as remarked by Solms-Laubach, there is no evidence that 

 the fructification belongs to the same species as the spine-bearing shoots. D. White 

 (1905, p. 61) has observed that the fragments of fertile »pinnae» from Gasjié »are distinctly 

 punctate and thus referable to the typical species ». With the delimitation of Psilophyton 

 princeps proposed in the present paper, however, not even this punctation can be consid- 

 ered as a proof of specific identity. In spite of the fact that the supposed fructifications 

 have been regarded as characteristic remains of Psilophyton princeps, it is necessary to 

 leave them out of consideration in order to arrive at an acceptable definition of the 

 species. 



In the same paper some rhizomes are described and figured which may really be- 

 tong to this species, though there is no proof of actual connection. The same remark 

 applies to the specimens showing anatomical structure figured and described as belong- 

 ing to the genus Psilophyton without being actually referred to this species. They will 

 be further considered below. 



The only specimens figured in the paper mentioned which should be regarded as 

 belonging to the real Psilophyton princeps are those representing spine-bearing branches 

 and shown in pl. 9, figs. 97 — 101, 104, 109, 110. These are described by Dawson as a 

 variety, Ps. princeps var. ornatwm, on account of the more perfect development of the 

 »leaves». These are evidently rigid and spine-like, rapidly tapering from a thick base, 

 and perpendicular to the axis; their length is equal to the breadth of the axis or usually 

 less. In pl. 11, fig. 129, there is a magnified leaf showing a fine longitudinal striation; 

 fig. 129 a is supposed to show cellulär structure and a stoma, but even a vivid imagina- 

 tion will fail to recognize this. If the spine-bearing stems described in 1871 as var. orna- 

 tum are compared with those figured in the first paper as Psilophyton princeps, allowance 

 must be made for the fact that the figures of these first type-specimens are very poor 

 and probably do not give any adequate idea of the material on which the species was 

 founded. The drawings of the branches with »adpressed leaves» in Dawson's first paper 

 do not appear at all convincing; also, in the diagnose of Psilophyton princeps given in 

 the report of 1871, the »leaves» are no longer stated to be adpressed. In speaking of the 

 variety ornatum, Dawson says (p. 39): »The leaves were, however, precisely of the same 

 character with those of P. princeps, . . . . » and further: »The present form must be re- 



