294 ON THE STEM IN CERTAIN SPECIES OF CARYOPHYLLE.E AND PLUMBAGINE^. 



EXPLANATION OE THE PLATES. 

 Tab. L. 



Acanthophyllum spinosum, C. A. M. 

 Fig. 1 . Portion of a young leafy shoot. 

 Fig. 2. Transverse section from a young intemode : a. cortical parenchyma ; b. zone of small and delicate 



cells (cambium region) ; c. wood which abounds in vessels of various calibre ; d. transversely 



lengthened pith-cavity, the cells partly obliterated. 

 Fig. 3. a. From a young intemode ; b. from the next below ; c. from the third — the dividing fissure has 



changed to an opposite direction ; d. traces of further lobing become apparent ; e. about Jgth of 



an inch lower ; /. point from which a branchlet is given off. 

 Fig. 4. Semi-diagrammatic section from a young shoot of the same, showing the division of the woody 



mass, and a ' generative zone' surrounding each portion. 

 Fig. 5. Transverse section from lower portion of twig, fig. 1. 

 Figs. 6 & 7- Sections from older stems. 



Fig. 8. Semi-diagrammatic and enlarged ; the vessels often cut the horizontal plane obliquely. 

 Fig. 9. Vertical section showing the vessels obliquely traversing the thin-walled tissue forming the mass 



of the older stems. 

 Fig. 10. Diagram from one of the upper branchlets of the twig, fig. 1. In the wood, which is very full 



of vessels — more so, I think, than I have represented — four nearly equal zones are to be counted ; 



through these the vessels are irregularly distributed. The zones are separated by lines of very 



narrow vessels, which, according to my observations, are true spirals. 



Acanthophyllum (sp. dub., Griffith's AfiFghan Coll. no. 1562). 

 Fig. 11. Thin sections, successively removed from an older stem. 

 Fig. 12. Transverse section enlarged: a. cortical parenchyma, with numerous concretions of oxalate of 



lime. 

 Fig. 13. Portion more highly magnified, with cords of thickened prosenchyma. 

 Figs. 14 & 15. Vertical sections showing ' slit-marked' and spiral vessels with prosenchyma. 

 Fig. ] 6. Pith, with oxalate of lime. 

 Fig. 17. Tangential section dividing a radial parenchymatous cord. 



Tab. LI. 



Acanthophyllum laxiflorum, Boiss. 

 Fig. 18. Transverse and, fig. 19, vertical sections of the stem. 



Acanthophyllum (sp. dub., Griffith's Affghan Coll. no. 1570). 

 Fig. 20. Transverse section. Fig. 21. Same more highly magnified. 



Acantholimon diapensioides, Boiss. 

 Fig. 22. Transverse section. Fig. 23. Same enlarged. 



Acantholimon (sp.A. tomentello aff.). 

 Fig. 24. Transverse and, fig. 25, vertical sections of portions of the stem. 



Armeria maritima, Willd. 

 Fig. 26. Transverse section from lower portion of the stem (passing into the root ?) . Fig. 27. From about Jth 



of an inch higher up. Fig. 28. Section showing numerous radial processes in the same plane. 

 Fig. 29. Magnified transverse section showing the distribution of the vessels and cords of thick-walled 



prosenchyma. 

 Fig. 30. Tangential section dividing a radial cord. 

 Fig. 31. Isolated cells from the pith. 



