112 REPORT— 1871. 



a central medullaiy axis of cellular tissue with several detached longitudinal 

 buudles of vascular tissue at its circumference. Outside this is a lax lig;neous zone, 

 to the interior of which the bundles just referred to are adherent. The vessels of 

 the ligneous zone are reticulated, and arranged in radiating series, the radiating 

 lamina? being separated at very frequent intervals by thick cellular medullary rays, 

 consisting of numerous vertical series of cells. External to the woody zone is a 

 very thick and characteristic bark, the inner portion of which is loosely cellular, 

 but the exterior has a different structure. It consists of a combination of cellular 

 parenchyma and dense elongated prosenchyma, the latter appearing in the trans- 

 verse section as a series of dark bands, radiating at varying angles from the inner 

 to the epidermal layer of the outer bark. Vertically these prosenchymatous bands 

 are prolonged as layers, which extend upwards and downwards in a wavy manner, 

 alternately approaching and receding from one another, so that a tangential section 

 exhibits a series of lenticular areolae whose longer axes correspond with that of the 

 stem. The outermost bark-layer appears to be a cellular epidermal tissue, which 

 has probably supported external appendages, either scales or leaves. In the inner 

 layer of the bark we see a series of variously developed vascular bundles which 

 spring as branches from the ligneous zone, but which ascend for a considerable 

 distance without escaping through the bark, whilst a second series of branches are 

 given off in like manner, but which at ouce perforate the bark in their passage out- 

 wards. This plant is from the lower coal-measures of Lancashire and Yorkshire. 



A second form of Dictyoxi/lon, to which the author gives the name of D. radicmis, 

 has evidently been a branching root which has been traced continuously into its 

 ultimate rootlets. This plant has no pith, and its compact woody zone, consisting 

 of reticulated vessels, is furnished with medullary rays of a much simpler con- 

 struction than those of D. Oldhamium. They are not unfrequently represented in 

 the tangential section by a single cell ; and there are rfirely more than five or six 

 such cells in each vertical pile. The bark consists of parench-^Tnatous cells aiTanged 

 in rows perpendicular to the surface. This is also a Lancashire form. 



A third species of Dictyoxijlon discovered in beds of the lower Carboniferous 

 series of Bm-ntisland is named D. Gn'evii after its discoverer, Mr. Grieve. Its 

 central axis is much deranged, resembling the Heterangium paradoxum of Corda ; 

 but several specimens have occurred showing that there was a central vascular axis 

 surrounded by a lax radiating ligneous zone, which in turn was invested by a re- 

 markable cellular bark, which exhibited, both in radiating and tangential sections, a 

 characteristic series of parallel horizontal lines, resulting from a peculiar condition 

 of the cellular parenchyma at the points where they exist. As in D. Oldha7nium, 

 vascular bundles ascend through the inner bark. The plants described were con- 

 nected by the author with some large casts of bark fi'om the Coal-measures, some ot 

 which have been described as Sagenarire and Lyginodendra. These specimens have 

 upon their surface elongated lenticular scars arranged as in Lepidodendron ; but 

 usually much more elongated in a vertical direction than in that genus, and always 

 lacking the central spots marking the issue of vascular bundles. These areolre are 

 not leaf-scars, bvit casts of depressions in the outer surface of the bark from which 

 the epidennis was removed, and which con'espond with the spaces enclosed by the 

 sinuosities of the proseuchj-matous layers. The functional uses of these areolaj are 

 undetermined, and there is as yet much uncertainty as to the true affinities of the 

 genus. 



On the Strmiure o/" Diijloxylon, a Plant of the Carbonifei'ous Jiocls. 

 By Professor W. C. Williamson, F.B.S. 



On the Discovery of a new and very x>erfect Araclinide from the Ironstone of 

 the Dudley Coal-field. By Henry Woodavaed, F.O.S., F.Z.S., S(c., of the 

 British Museum, 



The Penny-stone Ironstone of the Coalbrook Dale Coal-field has long been cele- 

 brated for yielding, when the nodules are split, impressions of leaves of fernS; 

 Lepidostrohi and other fruits, King-crabs, and the rare remains of Insects. 



