XXXIlJ CLADOXYLON 205 



also the form of the trace given off from the stem of Aster ochlaena. 

 Solms 1 , while admitting that Bertrand may be correct in uniting 

 under one genus Cladoxylon and such types as Syncardia, Hiero- 

 gramma, and Arctopodium, disagrees with the view that they 

 are Clepsydropsis stems. A Clepsydropsoid leaf -trace has never 

 been found in direct association with any of the stems of the 

 Cladoxylon type and such evidence as there is indicates a leaf- 

 trace of an entirely different form (fig. 459, E). In his more 

 recent memoir on Asterochlaena Bertrand 2 draws attention to 

 Solms' figures of a stele of Cladoxylon (fig. 459, C) in which the 

 distal portion is on the point of being separated as a small annular 

 strand. This, Bertrand considers, would gradually become con- 

 verted into a Clepsydropsis form of stele as it passed to the 

 petiole. Bertrand's drawings made from a section of Cladoxylon 

 taeniatum (Ung.) (fig. 459, G) illustrate successive stages in the 

 departure of a leaf-trace from one of the plate-like steles of the 

 stem (fig. 459, B). In fig. 459, G, 1, a piece of the stele is detached 

 and near its extremity is a group of thin- walled cells with proto- 

 xylem : a later stage is seen in fig. 2, and in fig. 3 a small ring of 

 xylem is being detached which, Bertrand assumes, would later in its 

 course be converted into the Clepsydropsoid strand (fig. 4), which 

 consists of primary tissue. The weak point in Bertrand's contention 3 

 is the absence of any proof of a true Clepsydropsoid trace in con- 

 nexion with a Cladoxylon stem, and there is a strong probability that 

 the leaf -trace of Cladoxylon has the form shown in fig. 459, E. 



Cladoxylon Kidstoni Solms-Laubach 4 . 



This species, founded on imperfectly preserved material in 

 Dr Kidston's collection from Lower Carboniferous rocks in Berwick- 

 shire, is referred to Cladoxylon on evidence that cannot be regarded 



1 Solms-Laubach (10) p. 540. 2 Bertrand, P. (11) p. 47. 



3 Since this account was printed my attention has been drawn by Dr Scott to 

 a note by Bertrand in which he considerably modifies his views. He finds that 

 Hierogramma and Syncardia are probably different states of the petiole of 

 Cladoxylon and while agreeing with Solms-Laubach's conclusions he has been able 

 to add important new facts. Bertrand has now given up the opinion that Clep- 

 sydropsis is the petiole of Cladoxylon. For further details students should consult 

 the preliminary note which it is hoped will be followed by a fully illustrated 

 memoir [Bertrand, P. (14)]. 



4 Solms-Laubach (10) p. 537, PI. m. figs. 7, 11, 13. 



