PLATE IX. 



Fig. 12. — Tangential section of part of a xylem cylinder, made close to the 

 medulla, giving a transverse section of a primary medullary ray, b, and the 

 vascular rootlet bundle, /, /'. Enlarged secondary medullary rays at the orienta- 

 tion of the younger part of the rootlet bundle, d. X 30. Cabinet, No. 851. 

 (Pages 14, 23.) 



Fig. 18. — Transverse section of an extremely young root of Stigmaria. Vascular 

 wedges of the disturbed vascular cylinder, b. Superficial parenchyma of the cortex, 

 d. Cortical prosenchyma, d'. Rootlets belonging to the root, g, g. X 11. 

 Cabinet, No. 775. (Pages 15, 18, 42.) 



Fig. 34. — Another section like figs. 28 — 33, Plate IV, but with all its newest 

 small vessels derived from a half-developed exogenous zone like Fig. 19, b\ PI. IV. 

 X 80. (Page 23.) 



Fig. 35. — A wedge-shaped rootlet bundle from the same position as the pre- 

 ceding ones, but from the exterior of the large vascular cylinder from Staffordshire. 

 Protoxylem vessels,/'. X 80. Cabinet, No. 750. (Pages 23, 24.) 



Fig. 51. — Transverse section of a rootlet made about half way up the conical 

 portion, h', of the rootlet cushion. The outermost parenchyma of the root-bark, 

 d. The cortical layer of the rootlet, g. The second cellular layer of the rootlet 

 very rarely preserved, g . Section of the small cells of the rootlet cushion, h". 

 Rootlet bundle and its sheath, /. X 50. Cabinet, No. 821. (Page 27.) 



Fig. 52. — Centre of Fig. 51. Xylem portion of the rootlet bundle, /. 

 Phloem area of the bundle, /'. Bundle sheath,/", x 440. (Pages 28, 32.) 



