xcii PBOCEEDENGS OF THE GEOLOGICAL SOCIETY. [vol. lxxix, 



Having given some account of the Rhyme plants, I will now 

 consider the older Devonian floras as a whole. 



Many fossils from Scotland and other regions have heen errone- 

 ously assigned to Psilopliyton : though a characteristic genus, it 

 is less common than is usually supposed. The generic name has 

 done duty for a variety of plant-fragments, with the result that the 

 importance of Sir William Dawson's account of the type-species 

 has not received its full share of credit. Psilopliyton princeps 

 Dawson, if I may cite the best-defined species, agrees very closely 

 with Rliynia in habit and in its grosser anatomical features : from 

 a horizontal rhizome were given off erect, dichotomously-branched 

 shoots bearing sporangia at the tips of some of the ultimate branch- 

 lets. Short spinous appendages, less regularly disposed than 

 ordinary leaves, characterize the erect branches : the spines have 

 been compared with the smaller hemispherical swellings of Rliynia 

 gwynne-vaughani, and some authors regard them as simple forms 

 of leaves. A preparation of a piece of a Canadian specimen of 

 Psilopliyton made by Mr. J. Walton, who recently developed a 

 method of separating the plant-substance from the surrounding 

 matrix, shows very clearly several apparently rigid spines standing 

 erect from the stem and suggesting emergences rather than leaves. 

 Arber believed Psilopliyton and Rliynia to be generically iden- 

 tical. The two undoubtedly are closely allied, as Kidston & Lang 

 have stated ; but, for the present at least, the retention of both 

 names is advisable. Mr. W. N. Edwards has succeeded in ob- 

 taining a preparation of the carbonized film of a piece of Psilo- 

 pliyton which shows epidermal cells and stomata apparently 

 identical with those of Rliynia. Psilopliyton occurs in the older 

 Devonian rocks of Norway, Scotland, Canada, and the Noi"th of 

 France : it is essentially characteristic of the Lower and Middle 

 Devonian floras ; but, as Dawson believed and Dr. Halle has re- 

 cently shown, it probably existed in Upper Silurian times. The 

 genus has also been recorded from Upper Devonian rocks, both in 

 France and in North America, but the evidence is not convincing. 



It is not my purpose to deal with individual genera in detail ; 

 but reference may be made to a form of Psilopliyton described by 

 Dr. Halle from the Lower Devonian of Norway as Psilopliyton 

 golclsclimiclti. This species, in other respects apparently identical 

 with Psilopliyton princeps Dawson, is characterized by the re- 

 peatedly bifurcate lateral branches. One of the problems with 



