﻿BIBLIOGRAPHY. 



wedge-like portions of vascular tissue, the rounded origin of which, internally, is well 

 defined ; these wedges are generally of equal or nearly equal size, but they occasionally 

 become confluent by the joining of two or more of them together. The form of the 

 space necessarily left, or interstices between the sections where these are distinct, varies a 

 little, in some cases being of nearly equal breadth throughout, and in others becoming 

 narrower outwards and appearing to terminate or contract about the middle of the 

 vascular tissue, beyond which they again frequently widen outwards : these spaces often 

 contain portions of oblique and smaller vascular cords, apparently arising at different 

 depths in the vertical cylinder, the origin and connection of which with the cylinder is 

 shown in the oblique section, where a single series of vessels is seen passing from it 

 surrounded by tissue of smaller diameter (pi. xxxviii, fig. 3 a). 



" In no specimen yet examined has the course of the oblique cords been absolutely 

 ascertained, but there can scarcely be any doubt, as suggested by Mr. Brown (to whom 

 we are also indebted for the above observations), that these vessels, after arising from the 

 cylinder, passed to the tubercles of the surface, through the thick cellular tissue which 

 once probably occupied the larger space in the original plant. The discovery of these 

 smaller oblique vessels is an interesting feature in the anatomy of Stigmaria ; and they 

 have also been pointed out by Mr. Brown as existing in Analathra ; and one of these 

 is actually figured by Mr. Witham in his work (pi. viii, fig. 10), but considered by him 

 (p. 41) as a section of a medullary ray. The analogous vessels existing in Lepidodendron 

 Harcoartii, as figured by Mr. Witham ('Trans. Nat. Hist. Soc. Newcastle,' 1832), 

 appear to arise from the outer part of the vascular cylinder. A somewhat similar division 

 is found in that division of Zgcopodiacea consisting of Psilotum and Tmesepteris ; in 

 those genera (according to Brongniart, ' Veg. Foss.,' vol. viii, pp. 44, 45) the vascular 

 cylinder from which the oblique cords proceed includes a central pith." 



6. Goeppert 1 (Roots) describes a very good specimen of Stigmaria with the pith 

 containing vascular bundles, interspersed in cellular tissue, and the structure of the 

 rootlets having an axis of vascular tubes, surrounded by cellular tissue. He appears 

 to have been the first author to publish information on the structure of those portions of 

 the root. 



7. Binney 2 (Roots) describes the Fossil Trees having Stigmaria roots in Littler's 

 quarry, near St. Helen's, Lancashire. 



8. Binney and Harkness 3 (Roots). — Further observations on the last-named speci- 

 mens. 



9. Cord a (Diploxylon). — Corda 4 describes the characters of his Diploxylon cyca- 

 deoidum: — "Truneus medullosus cylindricus ; decorticatus extus longitudinaliter obscure- 



1 'Les Genres des Plantes fossiles,' Bonn, 1841. 



2 'The London, Edinburgh, and Dublin Phil. Mag.,' ser. 3, vol. xxiv, p. 165, 1844. 



3 Ibid., vol. xxvii, p. 241, 1845. 



4 ' Beitriige zur Flora der Vorwelt,' Prague, 1845. 



17 



