102 MR. T. HICK OX A NEW FOSSIL PLANT. 



EXPLANATION OF THE PLATES. 



Plate XVI. 



Fig. 1. External aspect of the fossil. 



a. Tubercles. 



Fig. 2. Transverse section. 



p. Pith. 

 r. Projecting roots. 



vb. Vascular bundles of tbe ring. 



ab. Vascular bundles going to the appendages. 



/. Line of union of true cortex to the radicular tissues. 



e. Intrusions of true cortex into the radicular tissues. 



c. Intrusion of radicular tissues into the true cortex. 



a, 6, e, d. Successive layers of the true cortex. 



Plate XVII. 



Fig. 3. Portion of the vascular-bundle ring &c., enlarged. 



p. Pith. 



vb. Vascular bundle. 



mr. Medullary ray. 



c. Procanibium or cambium. 



jr. Xylem. 



ph. Phloem. 



pc. Pericycle. 



iz. Internal zone of radicular tissues. 

 Fig. 4- Portion of vascular-bundle ring, less enlarged than in fig. 4. and 



showing in addition 



ah. Vascular bundles leaving the ring. 



pc. Pericycle, a portion of which accompanies the retreating 



bundles. 

 Other references as in preceding figures. 

 Fig. 5. Inner portion of true cortex. 



a. Third layer from surface. 



b. Fourth layer from surface-periderm. 



c. Fifth layer from surface abutting on the radicular tissues. 

 Fig. 6. Enlarged view of one of the roots of the radicular tissues. 



J, ph. Xylem and phloem of the vascular bundle. 

 cp. Concentric parenchyma. 

 rp. Radial parenchyma. 

 p. Periderm — an incomplete ring. 

 f. Fissure. 

 Fig. 7. Section of root just before it becomes free. 



a. Thin layer of parenchyma immediately surrounding the vas- 

 cular bundle. 

 6. Thicker layer of larger, irregularly arranged cells. 



c. Thick-walled, perhaps sclerenchymatous layer. 



d. Outermost layer of thin-walled cells. 

 s. Sheath- like layer. 





