PLATE XVII. 



Halonia regularis. 



Fig. 1 (No. 36). A portion of a root, showing the depressed areolae with a central 

 raised pimple. From the Upper Brooksbottom seam of Coal, Lancashire. Natural 



size. 



Fig. 2. A transverse section of the same root, showing the medullary axis, the 

 woody cylinder, the parenchyma (passing gradually into prosenchyma), and the epidermis. 

 Magnified 5 diameters. 



Fig. 3. A transverse section of one of the raised papilla? in the areola?, showing the 

 vascular tubes surrounded by a space formerly occupied by orthosenchymatous tissue, and 

 succeeded by a zone of fine parenchyma. Magnified 20 diameters. 



Fig. 4 (No. 37). A forking portion of a root, from the Upper Brooksbottom seam 

 of Coal, Lancashire. Natural size. 



Fig. 5 is a transverse section of the root, showing the medulla and vascular cylinder 

 divided across, surrounded by the parenchymatous tissue, with the outer zone and the 

 thick epidermis. Magnified 5 diameters. 



Fig. G is a transverse section of the medulla and the woody cylinder ; the unshaded 

 portion indicates their division. Magnified 10 diameters. 



