THE PINNA-TRACE IN THE FERNS. 371 



going to the pinna, the rest remains as the new margin of the leaf-trace strand 

 (text-fig. 11, d, e). This process appears in the supply of the second pinna (text- 

 fig. 11, e,f, g), but in relation to the other of the two leaf-trace strands.* 



Still other examples illustrating the same process may be cited in Matonia 

 pectinata (Seward, '99) and Archangiopteris Henryi, Christ et Gies. (Gwynne- 

 Vatjghan, '05). In Matonia the incurved adaxial edges of the leaf-trace unite, 

 their margins extend laterally and pass with the lateral portions of the leaf-trace 

 into the pinnae (text-fig. 12). The pinnae are thus supplied with an internal system 

 which probably meets the demand for a considerable water-supply without unduly 





O 



Text- Fig. 12. — Diagram illustrating the division of the single petiolar stele into the 

 vascular strands of the pinnae. (After Seward. ) 



depleting the supply for the rest of the leaf. For the actual backs of the incurved 

 hooks remain intact and pass up the rachis to carry water past the point of pinna- 

 trace departure. This looks like a special case of the Gleichenia-type in which not 

 only must water be carried up past the pinnae for the needs of the higher parts of 

 the leaf, but where the pinnae must also be provided in quick succession with a good 

 water-supply. 



The pinna of Archangiopteris Henryi is supplied by strands which occupy much 



* Chrysler argues from similar processes in B. ternatum that we have in this reinforcement a relic of an earlier 

 system of passage of the margin along the face of the leaf-trace strand, such as we have already mentioned in B. 

 virginianum. He sees no possible use for the reinforcing strand, as it is not connected at its base with the leaf-trace, 

 and declares that it cannot convey water. But the structure of the tracheides in the Ferns is such that water might 

 quite well be conveyed laterally from tracheide to tracheide even where the sets of tracheides are not continuous at 

 their bases. Water can readily be deflected from the main strand into this reinforcing strand as soon as the two are 

 in lateral contact, and thus the effect of the drain on the water-supply by the pinna-departure may be compensated for. 



