92 MB. T. HICK ON A NEW FOSSIL PLANT 



most part filled wholly or partially with a black or brown 

 material. The cells of this layer are larger than those of i., and, 

 as far as can be made out, are less regularly arranged. The 

 contents of the cells gives the layer, when seen with the naked 

 eye or a hand -lens, the appearance of a dark line running near 

 the margin of the section (PL XVI. fig. 2, b). 



iii. The next layer is thicker than both the preceding ones, 

 reaching nearly 2 millim., and consisting of from 12 to 20 rows 

 of cells (PL XVII. fig. 5, a). These vary in size, becoming slightly 

 smaller inwards, are rounded or polygonal in shape, and exhibit 

 neither a definite arrangement nor any radial or tangential com- 

 pression. The average size is about 0'127 millim. by 0*085 millim. 



iv. A zone consisting of radially arranged rows of cells traceable 

 all round the sections except where they are incomplete (PL XVI. 

 figs. 2, e ; PL XVII. fig. 5, b). The thickness of the zone shows 

 some variation, and its limits are rather uncertain at some points ; 

 but in well-preserved parts the rows contain from 8 to 12 cells. 

 Prom the position and character of this zone, I am inclined to 

 regard it as a periderm, though there is no evidence that the cell- 

 walls are suberised. 



v. Beneath this periderm we have what is practically a conti- 

 nuation of the tissue described in iii., the two forming a single 

 zone in which the supposed periderm has arisen (PI. XVI. fig. 2, d ; 

 PI. XVII. fig. 5, c). The thickness of this inner portion varies 

 considerably in different parts of the section according as it is 

 encroached upon to a greater or less extent by the radicular 

 tissues. The cells increase in size from without inwards, but 

 their arrangement is irregular throughout. 



t Radicular Tissues.— It is difficult, if not impossible, to give 

 any adequate idea of the characters and grouping of these tissues 

 in words. As already stated, they include a number of root- 

 like structures, each of which contains a single vascular bundle 

 enclosed by a variable amount of parenchyma. Eunning irre- 

 gularly through the mass and dividing it into irregularly shaped 

 portions are numerous bands of tissue strongly resembling peri- 

 derm, some of which are accompanied by narrow fissures, especially 

 in the peripheral region (PI. XVI. fig. 2). In several instances the 

 portions of tissue enclosed bv these fissures or peridermal bands 

 contain one of the bundles mentioned, so that the whole presents 

 the appearance of a number of roots whose peripheral tissues have 

 become closely pressed together or even organically united. 



Th 



