332 DR D. H. SCOTT ON THE 



The importance of the fossils now to be described consists in their showing the 

 primaiy structure of the wood ; in all of them there is proof of the existence, within 

 the zone of secondary wood, of distinct strands of primary xylem, resembling more or 

 Jess closely those which have long been known in the stems of the Lyginodendrese and 

 Poroxylese. This structure co-exists with secondary wood of the Dadoxylon type, in 

 some cases agreeing exactly with the wood which is known to have belonged to the 

 stems of Cordaitese.* Thus these fossils tend to establish a connection between the 

 stems of Palaeozoic Gymnosperms and those of certain Cycadofilices, and so to throw new 

 light on the question of the Filicinean origin of the Gymnospermous Phanerogams. 

 The subject of the course of the leaf-traces is closely connected with that of the primary 

 wood-strands, and is dealt with below so far as the material afforded data. Other 

 characters are considered incidentally. At the close of the paper the theoretical 

 bearings of the structural features in question are discussed. 



I. Calamopitys, Unger. 



1. Calamopitys fascicular is, sp. n. 



This is the stem described in my Note of 1899 under the provisional name of 

 Araucarioxylon fasciculare. The reasons for now placing the fossil in Unger's genus 

 will become apparent when the structure has been described. As mentioned in the 

 Preliminary Note, two specimens have been examined ; the first which came under 

 investigation is in the collection of Mr Kidston, and was found in 1898 by Mr John 

 Renwick at the Loch Humphrey Burn in the Kilpatrick Hills, Dumbartonshire. The 

 horizon is that of the Calciferous Sandstone Series. Mr Kidston very kindly placed 

 his sections at my disposal for investigation, and also allowed me to have some 

 additional sections cut from the remainder of the block. 



The second specimen is one of which the sections are preserved in the Williamson 

 Collection under the generic name Dadoxylon. The structure is identical with that of 

 Mr Kidston's stem (cf. PL I. phot. 1 and PI. III. fig. l). The Williamson specimen is 

 described in his MS. catalogue as being derived from the Carboniferous Limestone near 

 Haltwhistle. Thus both specimens are of Lower Carboniferous age. This plant, like the 

 other species to be described, combines an Araucarian type of secondary wood with the 

 presence of distinct primary strands of xylem around the pith. It is characterised by 

 the small diameter of the pith, the small number and relatively large size of the primary 

 xylem-strands, the simple leaf-traces, and the narrow medullary rays, giving the 

 secondary wood a Cordaitean character. 



The diameter of the pith is only about 2 mm. in Mr Kidston's specimen, and about 

 3 mm. in the Williamson example. The whole specimen reaches a maximum diameter 



* On the Cordaiteae, see Grand' Eury, Flore carbonifere du Departement de la Loire, 1877 ; Renault, Structure 

 compare de quelques Tiges de la 'Flore carbonifere, 1879 ; Cours de Bot. Fossile, t. i., 1881. A general account of the 

 family is given in Solms-Laubach's Fossil Botany, chap, v., Eng. trans!., 1891, and in my Studies in Fossil Botany, 

 Lecture XII., 1900. 



