STRUCTURE OF STIGMARIA. 439 



lary rays (a). Fig. 7, anterior (or circumferential) end of vascular 

 axis ; a, vessels passing through the medullary rays to the rootlets ; 

 b, vascular tissue of wood ; d, bundles of small vessels towards circum- 

 ference. Fig. 8, very highly magnified view of one of the narrow 

 medullary rays (fig. 6 c), forming a bundle of tubes of less diameter 

 than those forming the wood. Fig. 9, vertical section through the axis 

 of fig. 5. Fig. 10, magnified portion of fig. 9, showing at a the longi- 

 tudinal vessels of the wood ; at b, the horizontal ones passing through 

 the medullary rays. Fig. 11, another magnified portion from the cir- 

 cumference of the same ; a, the longitudinal vessels displaced by the 

 horizontal ones, b, which are fractured in the fossil, and pass upwards 

 towards the rootlets at b'. Fig. 12, section of the axis (fig. 5) taken at 

 right angles to the medullary rays. Fig. 13, very highly magnified 

 portion of ditto, showing the longitudinal vessels of the wood, a, dis- 

 placed by the horizontal ones, b, whose mouths are cut across, issuing 

 through the medullary rays. Fig. 14, horizontal section of another 

 axis, from a specimen marked externally as in fig. 4, and whose structure 

 accords with that of figs. 5 — 13. 



