i 9 i 5 ] PETRY—OPHIOCLOSSACEAE 365 



Fig. 9. — Transverse section of a stele of B. obliquum, showing tracheitis 

 scattered through the pith; X20. 



Fig. 10. — Transverse section of a portion of the stele of an injured rhizome 

 of B. obliquum, showing development of new vascular elements in connection 

 with the formation of a branch: ex', centripetal secondary xylem; ax', acces- 

 sory secondary xylem ; px, pericyclic xylem; s, sieve tubes; />, periderm; X27. 



Fig. 11. — Transverse section of a portion of the stele shown in fig. 10, at 

 a lower level, and showing detail of the vascular elements in the pith; ex, 

 centripetal primary xylem; X48. 



Fig. 12. — Transverse section of a portion of a stele of B. virginianum, 

 showing secondary xylem in the pericycle: pc, pericyclic cambium; e, endo- 

 dermis; X48. 



Fig. 13. — Transverse section through the apical region of a rhizome of 

 B. obliquum: a, apical cell; m, procambium of the youngest leaf; n, procam- 

 bium of the next older leaf; X 122. 



Fig. 14. — Longitudinal section through the apical region of a rhizome of 

 B. obliquum: b, axillary bud of second leaf; X122. 



Fig. 15. — Longitudinal section through the apical region of the rhizome 

 of B. obliquum: b, axillary bud of the youngest leaf ; X122. 



Fig. 16. — Longitudinal section through axillary bud of B. obliquum; 

 X48. 



Fig. 17. — Longitudinal section of mature bud of B. obliquum; X48. 



Fig. 18. — Transverse section of axillary bud near its base, as seen in a 

 tangential section of the rhizome: //, trace of the subtending leaf; X48. 



Fig. 19. — Transverse section of bud near the surface of the rhizome; X48. 



