1915] PETRY—OPHIOGLOSSACEAE 365 
Fic. 9.—Transverse section of a stele of B. obliquum, showing tracheids 
scattered aah the pith; X20. 
IG. 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: cx’, centripetal secondary xylem; ax’, acces- 
sory secondary xylem; px, pericyclic xylem; s, sieve tubes; p, periderm; X 27. 
G. 11.—Transverse section of a portion of the stele shown in fig. ro, at 
a lower level, and serie detail of the vascular elements in the pith; cx, 
centripetal primary xylem; X48. 
IG. 12.—Transverse ween: of a portion of a stele of B. virginianum, 
showing secondary xylem in the pericycle: pc, pericyclic cambium; e, endo- 
dermis; 
16. 13.—Transverse section through the apical region of a rhizome of 
_ B. obliquum: a, apical cell; m, procambium of the youngest leaf; ”, procam- 
bium of the next older leaf; 122. 
Fic. 14.—Longitudinal section through the apical region of a rhizome of 
B. obliquum: b, axillary bud of second leaf; X122. 
Fic. 15.—Longitudinal section through the apical ae of the rhizome 
of B. obliquum: b, axillary bud of the youngest leaf; X12 
Fic. 16.—Longitudinal section through axillary dase of B. obliquum; 
8 
Fic. 17.—Longitudinal section of mature bud of B. obliquum; X 48. 
Fic. 18.—Transverse section of axillary bud near its base, as seen in a 
tangential section of the rhizome: /é, trace of the subtending leaf; x48. 
Fic., 19.—Transverse section of bud near the surface of the rhizome; X 48. 
