674 Marsh . — The Anatomy of some Xer op hit oils Species of 
A further link in this chain of variation in stelar anatomy in § Pkysa- 
pteris is provided by Cheilanthes lendigera , another species of this 
section which is described by Gwynne-Vaughan (2). In this, so far as the 
endodermis and pericycle are concerned, each leaf-gap in the stele is closed 
up before the next above is formed. The leaf-gap in the xylem, however, 
remains open until it overlaps the gap formed in the xylem by the departure 
of the next leaf-trace above. In this manner a small separate xylem strand 
Fig. 3. Cheilanthes gracillima. Series of transverse sections of stem in acropetal order. 
In this and in Figs. 4, 5, 6, leaf-traces are represented in solid black. 
is formed within the stele, which crosses over at each leaf-insertion in just 
the same way as does the free dorsal meristele of so many of the simpler 
dorsiventral dictyosteles. 
In the genus Pellaea considerable variation in stelar anatomy also 
takes place. Pellaea falcata is a simple solenostele, and is mentioned as 
such by Gwynne-Vaughan, who also describes P. rotundifolia and P. andro- 
medaefolia as examples of the simpler form of transition from solenostely 
