178 



MEGALOXYLEAE 



CH. 



much narrower and have the form of ordinary water-conducting 

 elements. On one side of the primary xylem in fig. 447 an oval 

 and more compact group of narrow and longer tracheids is seen 

 at It 1 ; this is a leaf-trace about to enter the secondary- xylem 



B 



FIG. 448. Megaloxylon Scotti. A, transverse section at the junction of the 

 primary and secondary tissues ; B. longitudinal section showing the inner 

 edge of the secondary xylem, a; 2 , a leaf -trace, It, and the metaxylem, m. 



cylinder on its outward course. The same leaf-trace is shown 

 at U in fig. 446, B ; as it descends the trace becomes less distinct 

 and its elongated elements gradually merge into the general 

 mass of metaxylem. A portion of this leaf -trace is seen in fig. 



