LYGINODENDRON 



375 



that they might belong to Lyginodendron oldhamium, 

 an opinion which has since been raised to a certainty, 

 by the discovery, in many instances, of the stem and 

 petiole in actual connection (see Fig. 138, which shows 

 the stem and petiole in radial section through the 

 node). Before this discovery, the petioles were named 



Fig. 139. — Lyginadendron oldliamium. Transverse section of rachis. .r, V-shaped 

 xylem ; ph, phloem, completely surrounding xylem, forming the concentric bundle 

 v.b. ; ky, hypoderma. X about 35. From a photograph. Phil. Trans., W. and S. 

 Will. Coll. 145. 



Racliiopteris aspera. The petiole, which forked at some 

 distance from the stem, to form two equal main 

 branches of the rachis, contains either two distinct 

 vascular bundles, or a single fused bundle, having the 

 form in transverse section of a V or a W. In the finer 

 branches of the rachis, the single V-shaped bundle is 

 constant (see Fig. 139). The structure is in all cases 

 concentric, the phloem completely surrounding the 



