496 STUDIES IN FOSSIL BOTANY 



coalescence of the adjacent edges of the interrupted 

 zone of primary wood. It is only in this region, that 

 any indication of protoxylem-elements has been detected. 



The stem gave off branches, of much smaller size 

 than the main axis. The whole structure is quite 

 peculiar : the arrangement of the primary tissues points 

 clearly to Filicinean affinities, while the secondary 

 tissues have a Gymnospermous, though by no means 

 a specially Cycadean, character. The organisation 

 departs widely from that of the Lyginodendreae, 

 notably in the distichous arrangement of the leaves. 

 We can only agree with Count Solms, in regarding this 

 plant as the representative of a distinct family, forming 

 one more of those Palaeozoic types which combine the 

 characters of Filicineae and Gymnosperms. Protopitys is 

 thus an isolated genus, the relation of which to the other 

 groups described in this chapter is doubtful, though its 

 provisional place is clearly among the Cycadofilices. 



Another species has since been discovered by Mr. 

 Kidston in the Yoredale Rocks of Yorkshire, but has 

 not yet been described. 



CLADOXYLEAE 



Before ■ leaving the Cycadofilices, it will be well to 

 refer shortly to an interesting group of early Palaeozoic 

 plants, which have long been known, but the true 

 structure of which was only cleared up in 1897, by the 

 investigations of Count Solms-Laubach. 1 



The fossils in question, belonging to the genus 

 Cladoxylon of Unger, were found in Thuringia, at the 

 1 " Pflanzenreste des Unterculm von Saalfeld," above cited. 



