1919I BAILEY— BARS OF SAN 10 467 



primary pit areas; portions of bandlike thickenings of middle lamella visible 

 between rows of bordered pits; X300. 



■ Fig. 6(2. — Todea hymenophylloides: showing alternating arrangement of 

 bordered pits and anastomosing of bandlike thickenings of middle lamella; 



X300- 



Fig. 7. — Acrostichum sorbifolium Linn.: lateral facet of tracheid, showing 

 small, circular, bordered pits and biconcave thickening of middle lamella^ 

 latter somewhat indistinct owing to thickness of superimposed secondary wall; 

 X8cx>. 



Fig. 8. — Cercidiphyllum japonicum Sieb. and Zucc: lateral facet of 

 vessel segment, showing persistence of scalariform primary pit-areas after 

 more or less complete disappearance of bordered pits; Xsoo- 



Fig. 9. — Magnolia macrophylla Michx.: lateral facet of vessel segment, 

 showing unconformity between primary and secondary pitting. 



Fig. 10. — Asimina triloba (Linn) Dun.: lateral facet of vessel segment, 

 showing alternate multiseriate pitting; X300. 



Fig. II. — Cercidiphyllum japonicum: lateral facet of vessel segment, 

 showing transitional types of bordered pitting and imconformity between 

 primary and secondary walls ; X400- 



Fig. 12. — Cercidiphyllum japonicum: lateral facet of vessel segment, 

 showing unconformity between pitting of primary and secondary walls; X40o- 



PLATE XIV 



Fig. 13. — Agathis auslralis Steud.: pitting in radial facet of tracheid, 

 showing "alternating" type of arrangement; X3SO- 



Fig. i4.—Cycadeoidea Dartoni (Coult. and Chamb.) Wiel.: radial longi- 

 tudinal section of secondary xylem, showing transitional types of pitting; 

 Xioo. 



Fig. 15. — Trochodendron aralioides Sieb. and Zucc: radial facets of 2 

 tracheids, showing transitions between scalariform and opposite bordered 

 pitting; Querleislen appear as narrow dark lines separating scalariform pits 

 or pairs of smaller bordered pits; X350. 



Fig. 16. — Trochodendron aralioides: radial longitudinal section of second- 

 ary xylem, showing transitional types of pitting and (right) persistence of 

 scalariform primary pit areas with reduction in number of bordered pits; 

 X200. 



Fig. 17.— Ulmus americana Linn.: tangential longitudinal section of 

 cambium (winter condition), showing knotenjormige thickenings of middle 

 lamella; X230. 



Fig. 18. — Ulmus americana: radial longitudinal section of cambium and 

 young phloem cells, showing sculpture of middle lamella; X200. 



Fig. 19. — Pteris aquilina Linn.: adjacent walls of 2 tracheids in sectional 

 view, showing knotenjormige thickenings ("bars of Sanio") of middle lamella; 

 X300. 



