DESCRIPTIVE INDEX TO THE PLATES. 



59 



'IO. 



PLATE 



28. x 





29. 





30. 

 31. 



y v. 



32. 





33 J 





34. 



IX 



35. 



IX 



36. 



XI. 



37. 



39. 



H). 



13. 



11 



1.3. 



XII. 



XII. 



XII. 



XII. 



XII. 

 X. 



X. 



VI. 



Transverse sections of six rootlet bundles after they have escaped from the peri- 

 pheral ends of the primary medullary rays, but before they have penetrated the 

 cortex. In each of these, f indicates the protoxylem of the wedge-shaped 

 bundle and the broad opposite base of the wedge, including the small vessels, 

 /, its latest additions, x 80. Cabinet, No. 744 . . 23, 24 



Another section like Figs. 28 — 33, but with all its newest small vessels derived 



from a half developed exogenous zone like Fig. 19, V , PI. IV. x SO .23 



'Two wedge-shaped rootlet bundles from the same position as the preceding ones, 

 but from the exterior of the large vascular cylinder from Staffordshire. Proto- 

 xylem vessels,/', x 80. Cabinet, No. 750 . . . 23, 24 



Part of a fragment of a Stigmarian root split vertically. Exterior of the vascular 

 cylinder, b'. Eootlet bundles crossing the cortical region,/". Exterior surface 

 of the cortex, d, d. Half the natural size . . . .24 



One extremity of Fig. 39. Vascular wedges, b, of the cylinder separated by primary 

 medullary rays, V . The central medullary cavity is occupied by an intruded 

 Stigmarian rootlet, in the interior of which the rootlet bundle is preserved. 

 Nat. size. Cabinet, No. 867 .... . 24 



Side view of Pig. 38, with numerous rootlet bundles,/) enclosed within their several 

 bundle sheaths, issuing from the primary medullary rays of the cylinder. Nat. 

 size. Cabinet, No. 867 . 24, 26 



Fragment of a large nodule enclosing a disorganised Stigmarian root, almost identical 

 with one of which the specimen, Figs. 38, 39, is the vascular cylinder, d repre- 

 sents a cast of the outer surface of one side of the root, with casts of the basal 

 ends of the rootlets penetrating the stone. Eootlets from the opposite side of 

 the root are seen at g, g, with their free ends pointing to the right, f, a mass of 

 rootlet bundles resembling these given off from the exterior of Fig. 39 . 39 



Inner surface of a fragment of the outermost bark, with rootlet bundles penetrat- 

 ing it to reach the rootlet-scars existing on the reverse side of the specimen . 25 



Transverse section of a large Stigmarian rootlet, g, into the interior of which 

 several other younger rootlets have penetrated. Vascular bundle of the large 

 rootlet,/. Cortex of one of the smaller rootlets, g". Its inner vacant cavity, 

 g'. Its vascular bundle and sheath,/', x 11. Cabinet, No. 848 . 25, 33 



Longitudinal section of the proximal end of a rootlet. Parenchymatous cortex of 

 the root, d, d. Prosenchymatous cortex of the root, e. Vascular rootlet bundle, 

 // Eootlet bundle-sheath,/. Branching cells investing the extremity of 

 the rootlet cushion, i, i. Outer cortex of the rootlet, g, (/. Fistular interior 

 of the rootlet, /. x 18 . . . . . 26, 27, 28 



Longitudinal section of the proximal end of another rootlet. Prosenchymatous 

 zone of the root-bark, d'. Central portion of the rootlet cushion, h, h. Conical 

 extremity of the rootlet cushion inside the rootlet, h! . Eootlet bundle, / 

 Eootlet bundle-sheath, f. Outer cortex of the rootlet, g. Fistular interior 

 of the rootlet, g' . X 18. Cabinet, No. 819 . . 26, 27, 28 



Longitudinal section of the proximal end of another rootlet. Parenchymatous 

 zone of the root-bark, d, d. Eootlet bundle,/, enclosed by its rootlet bundle- 

 sheath, /'", and passing outwards through the rootlet cushion, h, k. Apex of the 

 rootlet cushion, h'. Outer cortical zone of the rootlet, g. x 18 . 19, 26 



