Kaloxylon Hookeri and Lyginodendron Oldhamium. 109 



On Kaloxylon Hookeri, Will, and Lyginodendron Oldhamium, 

 Will. By Thomas Hick, B.A., B.Sc, A.L.S., 

 Assistant Lecturer in Botany, Owens College. 

 Communicated by F. E. Weiss, B.Sc, Professor 

 of Botany at the Owens College. , 



{Received May Jist, iSp^..) 



In the Vllth and Xlllth of his Memoirs "On the 

 Organisation of The Fossil Plants of the Coal Measures," * 

 Prof. Williamson describes a number of fossilised plant 

 remains under the name of Kaloxylon Hookeri. The fossils 

 obviously represent fragments of the axial parts of some 

 plant or other, and the structure they exhibit is somewhat 

 striking even among Carboniferous plants. Practically, 

 there are three series of specimens described, which 

 represent three stages of development of one and the same 

 structure, though, as we shall see, this is not apparent from 

 Williamson's descriptions. 



Taking first those which have reached the highest stage 

 of development, the main structural peculiarities, which 

 they present, as described by Williamson, are as follows : — 



1. A central cylinder composed of vascular elements inter- 

 mingled with delicate thin-walled cells. The former are of a type 

 which Williamson calls reticulated, but which I should prefer to 

 call pitted, and those at the periphery are usually of smaller 

 diameter than those nearer the centre. 



2. Enclosing the central cylinder are a variable number, 

 usually from four to six, of secondary, collateral, vascular bundles, 

 separated from one another by broad medullary rays, whose cells 

 are radially elongated. Each bundle has a well-marked phloem, 

 from which the centrifugally developed xylem was presumably 



* Phil. Trans., 1876. Ditto, 1887. 



