CALAMARIEAE. 303 



of its surface. Exactly similar pictures result when the outer surface of the 

 woody body deprived of the rind is disclosed to view, as is the case with 

 a piece of petrified wood of Arthropitys from St. Berain (Saone et Loire) in 

 my possession. Unfortunately this piece of wood, which is as thick as an 

 arm, though it shows the wedges on the face of the section, is too badly 

 preserved for microscopical examination 1 . I have verified this specimen 

 by comparison with two others from the calcareous nodules of Langendreer 

 and Oldham, thebest of which is kept in the Museum at Strassburg. But 

 in these, in contrast with the cast, the ridges on the surface, which is marked 

 by slightly sinuous furrows, answer to the somewhat convex outer faces of 

 the wedges of wood, the furrows to the rays. The Strassburg specimen 

 shows a nodal line tolerably distinctly as a transverse swelling. A still finer 

 piece from Oldham also showing a node may be seen in Binney 2 . 



Williamson 3 . Binney 4 , and Stur 5 have published longitudinal sections 

 through these nodes. Williamson's first figure is taken from a specimen 

 with a weakly developed woody body, elongated internodes, and the rind 

 preserved ; that of Stur, determined as Calamites approximatus, has quite 

 short internodes and numerous equidistant nodes ; its woody body is of 

 considerable thickness. A diaphragm stretches across the medullary cavity 

 at each node. This diaphragm is a parenchymatous structure of no slight 

 thickness, and in Stur's specimen it maintains this thickness in all parts, but 

 in Williamson's it fines down towards the centre into a thin lamina. In a 

 similar preparation in the collection of sections in the Botanical department 

 of the British Museum, a foliar bundle may be seen in exact longitudinal 

 section on the line of the diaphragm running towards the outside. But the 

 tangential sections are much more important and instructive when they pass 

 through a node, as happens in some of Williamson's figures c . From the 

 two figures especially in the first of the monographs, one of which is here 

 reproduced in Fig. 41 A, and in which the sections have encountered the 

 woody body in the neighbourhood of the pith where the primary rays are 

 broad and evident, we see that the position of the secondary wedges of wood 

 directly follows the original primary course of the strands. This course agrees 

 essentially with that of recent Equisetae. Each bundle passes downwards 

 through an internode, and then forks and unites by its limbs with the adjoin- 

 ing bundles in the node next below, which thus shows the well-known broken 

 zigzagged commissural-strand. In this process the descending bifurcating 

 strands are often split up in such a manner as to enclose a wedge-shaped space 

 with two pointed ends, which resembles a medullary ray and is filled with 

 parenchyma. And other sections in the ninth monograph, unfortunately of too 



1 Grand' Eury (1), p. 286. 2 Binney (1), I, t. 3, f. i. 3 Williamson (1), I, t. 24, 



f. 10, and ix, t. 20, .15. * Binney (1), I, t. 3, f. 3. 5 Stur (8), p. 459, f. 14. 



* Williamson (1\ I, t. 23, f. 2 ; t. 26, ff. 22, 25 ; ix, t. 20, ff. 23, 24, 29 ; t. 21, ff. 26, 28. 



