368 MR R. C. DAVIE ON 



as a closed ring. In Clepsydropsis the actual margin of the leaf-trace goes off to 

 supply a pinna ; in Anhyropteris the pinna-trace leaves the leaf-trace in the extra- 

 marginal way. 



Where there are two orthostichies of primary pinnae to be supplied from each arm of 

 the leaf-trace, as there are in Dineuron, Metaclepsydropsis, Diplolabis, and Etapteris, 

 the pinna-trace-bar leaves the leaf-trace on the side directed towards these pinnae 

 as a single curved mass of xylem, and then breaks into two parts, each of which moves 



ANNCAU 



REPARATRICE 



INTERNE 



PINNA I- -PINNA 



TRACE /A TRACE 



Text-Fig. 9. — Departure of pinna-trace in Anl-yropteris bibraclensis, var. westphalensis, P. Bertrand. 



(After P. Bkktrand. ) 



out to a pinna. Where the pinnae are uniseriate, as in Anhyropteris, the pinna-traces 

 depart from the edges of the leaf-trace at the ends nearest to the pinnae and move 

 directly out to them. In Tubicaulis solenites, Cotta (text-fig. 10, a) (the C faces 

 with its curve away from the axis — reverse of the living Fern), and in Anachoropteris 

 Decaisnei, B. Renault (text-fig. 10, b), the pinna-traces leave the leaf-traces back 

 from the edges, and the marginal set of tracheides is undisturbed throughout the 

 rachis. But the pinna-trace in these two is a solid patch of xylem and not a closed 

 ring. Bertrand makes a suggestive explanation of the Anachoropteris type, deriv- 



o 

 o 



O 



Text-Fig. 10. — Diagrams illustrating the departure of the pinna-trace in a, Tubicaulis solenites, Cotta ; 

 b, Anachoropteris Decaisnei, Renault. (Alter P. Beutrand.) 



ing it from the type of Dineuron pteroides by development of the anterior hooks. 

 He indicates how the position from which the pinna-trace departs in Anachoropteris 

 corresponds with that from which the Dineuron pinna-trace goes off from the leaf- 

 trace. This is an emphasis of the retention by the pinna-trace of the position of 

 departure relatively to the leaf- trace. The pinna-traces of Dineuron and Anaclio- 

 ropteris correspond to the marginal and extramarginal types in the living Ferns, 

 though we must remember that the Dineuron pinna-trace breaks into two parts after 

 Lining off from the leaf-trace, and that it has to supply two orthostichies of pinnae. 

 This caution also applies to the pinna-trace of Tubicaulis, though the trace of 

 Anachoropteris supplies but one pinna. Any discussion of the type of leaf in the 

 Zygopteridese and Botryopteridese as illustrated by these leaf-traces is out of place 



