THE PINNA-TRACE IN THE FERNS. 



359 



As the Marattian leaf-trace appears to be the horse-shoe type with much infolded 

 margins, the pinnae are supplied partly from the portions which correspond to the 

 backs of the hooked portion of the horse-shoe type and partly from the infolded 



Text-Fiu. 4. — Angiopteris evecta (Forst.) Hoffm. Diagrammatic representation of the process of supplying 



the basal pinna with its vascular system. 



margins, which are represented in the Marattian trace by the strands in the central 

 position. A gap is left in the leaf-trace for some distance above the pinna. This 

 is soon filled up by a movement into it of the leaf-trace strands at its edges and by 

 new strands nipped off from these. 



Text-Fig. 5. — Murattia attenuata, Lab. Diagrams illustrating the separation of the basal pinna-trace from 



the vascular strands of the petiole. 



A similar process is seen in the petiole of Helminthostachys zeylanica (L.) Hk. 

 There the pinna is supplied by strands which come partly from those forming the 

 outer ring, and partly from the internal petiolar strand (cf. G Wynne- Vaughan, 

 '05, p. 266). This type of pinna-supply can hardly be called either marginal or 

 extramarginal. 



The case of Helminthostachys is not typical for the Ophioglossacese, however, for 

 in Botrychium lunaria (L.) Sw. we do have a definitely marginal type of pinna- 



