374 MESSES. CTEIL WEST AND H. TAKEDA ON 



l'i«-. 11. Part of the same section, including the basal portion of the uppermost leaf-trace (on the left) 



and the adjacent stelar tissues. X 250. 

 Compare the size and shape of tracheids belonging to the leaf -trace and stele respectively. 

 Yi^. 12. Slightly oblique transverse section of a stem passing through the youngest part of the stele. 



X 250. Note the leaf-traces surrounding the stelar region, many of which are not yet 



differentiated. 

 Fig. 13. Part of a transverse section tlirougli tlie oldest part of tlie caudex showing connection of leaf- 

 trace with stem-stele. X 200. 



Plate 35. 



Fig. 14. Ditto, showing the horizontally stretched xylem parenchyma of the stem-stele. X 220. 

 Fi^.'lS. Part of a tangential section of the stem (cut in a plane immediately outside the stele) sliouing 



several leaf-traces cut transversely. X 220. 

 The phloem of the leaf-traces is shown in organic connection with that of the stem-stele. 



Note the deposits of callus. 

 Fig. 16. A similar section of the stem of Isoetes lacustris. X 285. 



Fig. 17. Part of a sieve-tube from the root, showing sieve-areas on the lateral walls. X 700. 

 Figs. 18 & 19. Sieve-tubes of the secondary phloem; from a transverse section of the stem. X 700. 



Note the callus deposited in some of the cells. 

 Fig. 20. Sieve-tubes of the secondary phloem of Isoetes lacustris ; from a longitudinal section of the 



stem. X 700. 

 Fig. 21. Part of a transverse section of the stem, passing through the junction of a leaf-trace with the 



stele. X 220. Note 

 the stem. 



that of 



Plate 36. 



Fig. 22- Transverse section through epidermis of the submerged portion of a leaf, x 450. 

 Fig. 23. Transverse section through epidermis of the aerial portion of a leaf. Two stomata are 



shown. X 450, 



Fig. 24. Stoma in surface view, x 220. 



Figs. 25 & 26. Basal portion of two sporophylls from the intermediate region of the ^rosette. 



Nat. size. 

 Fig. 27. Basal portion of one of the innermost leaves of the ' rosette.^ Nat. size. 

 Fig, 28. Stellate cells from leaf diaphragm, x 220. 



Fig. 29. A cell of the ligule. X 1000. Note the mucilaginous appearance of the cytophisni. 

 Fig. 30. Transverse section of the central region of a ligule. x 100. Note the irr< 



cells and intercellular spaces^ both of which may contain mucilage. 

 Fig. 31. Part of the above more highly magnified, x 220. 

 Fig. 32. Cells of the central region of the ligule in surface view, x 220. Note the characteristic 



t* 



wxvy^* yjM. ^^^^ xx^ 



intercellular spaces in the epidermis. 



Fig. 33. Fully developed ligule. x 6. 



Fig. 34. Marginal portion of the above more highly magnified, x 100. 



Figs. 35-40. Successive stages in the development of the ligule. x 285. 



