294 Royal Society. 



the stem of a tree fern, corresponding to those of the Psaronike 

 long known to characterize the upper Carboniferous deposits of 

 Autun and other localities. The roots of the Oldham specimen, 

 to which the author has assigned the name of Psaranites llenaultii, 

 •consist of a well-defined cylinder of sclerenchymatous prosen- 

 chyma, within which has been a mass of more delicate paren- 

 chyma, in the centre of which was the usual vascular bundle. But 

 what characterizes the specimens, distinguishing them from the 

 numerous species decsribed by Corda, is the existence of vast 

 numbers of cylindrical hairs, each composed of a linear row of 

 elongated cylindrical cells : these have obviously been the absorbent 

 root-hail's of the living plant, which may possibly have been some 

 species of Stemmatopteris ; but of this there is as yet no evidence. 



The author then describes a small but very remarkable stem, to 

 which he assigns the name of Kaloxijlon HooTceri. This is a slender 

 stem, rarely more than from one seventh to one tenth of an inch in 

 diameter. In its young state it consists of a central vascular axis 

 which has a hexagonal section, and which is composed of numerous 

 vessels of various sizes, each of which exhibits the reticulate form 

 of the scalariform or barred type, and which is so common amongst 

 the plants of the Coal-measures. No true barred or spiral vessels 

 have yet been seen in the Kaloxylon. In the young twigs this 

 vascular axis is surrounded by a mass of large-celled cortical 

 parenchyma, which, in turn, is encased by an epidermal structure, 

 composed of a double row of what have evidently been colourless 

 cells, and which are elongated vertically, but with square ends. 



In the more matured stems, the central vascular axis of the 

 young twigs becomes the centre whence radiate six exogenously 

 developed wedges of vascular tissue, each of which enlarges as it 

 proceeds outwards and terminates at its outer extremity in a 

 slightly rounded contour. Each wedge consists of a series of 

 radiating vascular lamina?, separated by numerous medullary rays, 

 which latter consist of long and, for the most part, single vertical 

 rows of mural cells. These six exogenous wedges are separated 

 from each other by a large wedge of cellular cortical parenchyma, 

 the cells of which are elongated radially and have a somewhat mural 

 arrangement. As those between any two contiguous wedges pro- 

 ceed outwards, they separate more or less definitely into two series, 

 which diverge right and left to sweep round the peripheral extremity 

 of each nearest 'exogenous wedge, meeting and blending with a 

 similar set coming from the opposite side of the wedge. In doing 

 this they form a sort of loop, enclosing a semilunar mass of smaller 

 cells interposed between the loop and the outer end of the exogenous 

 wedge. The author demonstrates that this enclosed cellular tissue 

 is essentially a cambial layer, out of which all the new vessels 

 and peripheral extensions of the medullary rays were developed. 

 Young vessels are seen at its inner surface in process of formation. 

 External to these two specialized cortical tissues there is, in these 

 matured stems, a mass of the primitive cortical parenchyma seen 



