88 MB. T. HICK ON A NEW FOSSIL PLANT 



cimen to 4| decimetres. There are no leaf-cushions at the outer 

 periphery; but in two of the sections what appear to be two 

 rootlets project from one side of it (PL XVI. fig. 2, r). 



Histology. 



Pith (PI. XVII. figs. 3, 4,^).— The pith is cellular throughout. 

 In the transverse section the cells are rounded or polygonal in 

 shape, and vary in diameter from 0*061 to 002 millim., or even 

 less, the larger and smaller being irregularly intermingled. 

 Intercellular spaces lie between them. The walls are not much 

 thickened, but are often irregularly folded, as if by external 

 pressure. Some of the cells are filled with a black substance 

 such as often occurs iu the tissues of Carboniferous plants, which 

 is probably of organic origin, though this is not certain. Save 

 this, there are no indications of any organic contents, the finely 

 granular appearance seen in some of the cells being: most likelv 

 due to infiltered mineral matter. The cells do not markedly 

 diminish in size towards the periphery, as do those of some Dicoty- 

 ledons, but the walls are thinner. 



In the longitudinal sections the cells are seen to be much 

 elongated longitudinally, the length reaching from 3 to 5 times 

 the transverse diameter. Tor the most part they run in linear 

 series, but this arrangement is here and there lost or obscured. 

 The end- walls are partly rectangular and partly oblique. 



Vascular Bundles.— It has been mentioned that the vascular 



bundles vary in breadth tangentially, owing apparently to lateral 



coalescence. The transverse sections suggest that some of the 



bundles are made up of two and others of three smaller bundles 



which have united in this way (PL XVII. fig. 3, vb). Further, 



the bundles vary somewhat in breadth and proximity as we 



pass from one section to another, indicating that in the short 



space between the sections they ran somewhat tangentially 

 oblique. 



Xylem.— As in most other Carboniferous plants, the xylem 

 part of the bundles is well preserved and is sharply differen- 

 tiated (figs. 3, 4, cc). It consists of trachea* of the scalariform 

 type, arranged in radial rows, in which the smaller are usually 

 near the pith, and the larger at the outer periphery. In some 



In De Bary's sense. 



Anatomy 



