772 de Bruyn.—Development of Stele in Two Species of Diptevis. 
nearer the lamina and ultimately branches dichotomously before the lamina 
is reached. The latest formed leaf-traces investigated depart from the 
edge of the leaf-gap as two successively separated cylindrical strands. 
This phenomenon may be connected with the more thorough dichotomous 
division of the leaves of D. Lobbiana. 
Botany School, Cambridge. 
March , 1911. 
EXPLANATION OF FIGURES IN PLATES LVII AND LVIII. 
Illustrating Miss de Bruyn’s paper on Dipteris. 
PLATE LVII. 
Fig. I. D. conjugata rhizome. Fairly young plant. Transverse section of the stele. Pith 
consisting of only one cell. x 340. 
Fig. 2. D. conjugata rhizome. Fairly young plant. Transverse section of the leaf-trace still 
in the main axis, x 340. 
Fig. 3. D. Lobbiana. Young plant, x 2. 
Fig. 4. D. Lobbiana rhizome, just above primary root. Transverse section of the stele, showing 
protostelic structure, x 290. 
Fig. 5. D. conjugata. One of the first-formed leaves, showing reticulate venation, x 8. 
Fig. 6. D . Lobbiana. One of the first-formed leaves, x 8. 
Fig. 7. D. Lobbiana rhizome. Fairly young plant. Transverse section of the stele. Only one 
internal endodermal cell, x 260. 
Fig. 8. D. Lobbiana rhizome. Young plant. Transverse section of the stele near the apex. 
Stele in meristematic condition, except one part of it, which forms a leaf-trace. x 260. 
Figs. 9, 10, 11, 12. D. Lobbiana rhizome. Older plant. Diagram showing the formation of 
the double leaf-trace. 
PLATE LVIII. 
Fig. 13. D. conjugata rhizome. Young plant. Transverse section of the stele, showing two 
dark internal cells, x 156. 
Fig. 14. D. conjugata rhizome. Same plant as Fig. 13. Section nearer to the apex. Trans¬ 
verse section of the stele, showing Lindsaya type and unequally developed xylem-ring. x 156. 
Fig. 15. D. Lobbiana rhizome. Young plant. Transverse section of the stele. Xylem in 
scattered groups. x 156. 
Fig. 16. D. Lobbiana rhizome. Same plant as Fig. 15. Section nearer to the apex. Trans¬ 
verse section of the stele. Xylem very much developed in connexion with root formation, x 156. 
Fig. 17. D. Lobbiana rhizome. Older plant. Transverse section of the stele, x 100. 
Fig. t8. D. Lobbiana petiole, 3*5 cm. in length. Transverse section of the stele near the base, 
x 156. 
Fig. 19. D. Lobbiana petiole. Same petiole as Fig. 18. Section at 1 cm. from the base. 
Transverse section of the stele, x 156. 
Fig. 20. D. Lobbiana petiole. Same petiole as Figs. 18 and 19. Section near the lamina. 
Transverse section of the bundles, x 156. 
