232 THE FOSSIL OSMUNDACE^. 



Fig. 6. Oismunda cinnamomea. Wall between two xylem elements. x 600. 



Fig. 7. Osmundites skidegatensis. Transverse section of the xylem showing the structure of the walls of 

 the tracheae, x 180. (Slide 1251.) 



Fig. 8. Zalesskya gracilis. Transverse sections of the walls of the xylem elements, a, a single series 

 of pits, each represented by a black line in the substance of the wall ; b, two series of pits ; c, ditto with an 

 additional small black line; d, three series of pits with additional small black lines; e and/, imperfectly 

 preserved walls. x about 600. 



Plate III. 



Fig. 9. Zalesskya gracilis. Transverse section of the peripheral tissues of the stele, xy. sh., zone of 

 parenchyma separating xylem from phloem; in. c, inner cortex. x 50. (Slide 1252.) 



Fig. 10. Zalesskya gracilis. Transverse section of the phloem; S. T., sieve-tubes; pel., pellicle within 

 the sieve-tubes; ph. par., phloem parenchyma; xy. sh., xylem sheath. x 260. (Slide 1252.) 



Fig. 11. Zalesskya gracilis. Transverse section of the periphery of the xylem showing a mesarch 

 protoxylem group. x 80. (Slide 1253.) 



Fig. 12. Zalesskya gracilis. Transverse section of the periphery of the xylem showing the first 

 indication of the departure of a leaf-trace. x 30. (Slide 1253.) 



Fig. 13. Zalesskya gracilis. The departing leaf-trace at a point higher up than that shown in fig. 12. 

 x 30. (Slide 1235.) 



Fig. 14. Zalesskya gracilis. The leaf-trace with its xylem just free from the xylem of the stele. x 30. 

 (Slide 1252.) 



Fig. 15 a and b. Zalesskya gracilis. Transverse sections of two different leaf-traces in close proximity 

 to the stele. The protoxylem is still mesarch. x 40. (Slide 1253.) 



Fig. 16. Zalesskya gracilis. Transverse section of a leaf-trace some distance out in the cortex, xy. sh., 

 xylem sheath ; ad. ph., adaxial phloem ; ah. ph., abaxial phloem ; era., endodermis. x 90. (Slide 1253.) 



Fig. 17. Zalesskya gracilis. Transverse section of one of the outermost leaf-traces in the specimen, 

 x about 12. (Siide 1253.) 



Fig. 18. Zalesskya gracilis. Transverse section of the periphery of the stele showing the departure of 

 the root steles; r. st., root steles. x 20. (Slide 1252.) 



Fig. 19. Zalesskya gracilis. Transverse section of a root when still in the cortex of the stem; sc. r., 

 sclerotic cortex of root, x 22. (Slide 1260.) 



Fig. 20. Zalesskya gracilis. Transverse section of the stele of the same root more highly magnified. 

 pr. ph., pro to phloem ; en., endodermis. x 110. (Slide 1260.) 



Plate IV. 



Fig. 21. Zalesskya diploxylon. External surface of the specimen. Nat. size. (Photograph by Mons. 

 R. Koch; forwarded by Mons. M. Zalessky.) 



Fig. 22. Zalesskya diploxylon. A complete transverse section of the specimen, st., stele, x about 2£. 

 (Slide 1268.) 



Fig. 23. Zalesskya diploxylon. Transverse section of a portion of the stele, o. xy., outer xylem ; 

 cen. xy., central xylem ; x., inner limit of outer xylem zone. x 30. (Slide 1268.) 



Fig. 24. Zalesskya diploxylon. Longitudinal section of the stele. Lettering as in fig. 23. x about 14. 

 (Slide 1271.) 



Fig. 25. Zalesskya diploxylon. Longitudinal section of a portion of the central xylem. x 35. 

 (Slide 1271.) 



Fig. 26. Zalesskya diploxylon. Transverse section of the peripheral tissues of the stele, car., zone of 

 carbonaceous matter, x 65. (Slide 1268.) 



Fig. 27. Zalesskya diploxylon. Transverse section of the periphery of the stele showing a departing 

 leaf-trace. x 30. (Slide 1268.) 



Fig. 28. Zalesskya diploxylon. Transverse section of a leaf-trace in the cortex of the stem. ad. ph., 

 adaxial phloem ; ah. ph., abaxial phloem ; car., ring of carbonaceous matter. x 30. (Slide 1269.) 





