The wood of stems of the Calamitina group of _Calamites_, in some instances at least, was of the _Arthropitys_ type; this has been shown to be the case in some French specimens from the Commentry coal-field[771] and in others described by Stur[772]. The pith-casts of _Calamitina_ are characterised by comparatively short internodes separated by deep nodal constrictions, as shown in fig. 100. From Permian specimens from Neu Paka in Bohemia, described by Stur[773], we learn that there were the usual Calamite diaphragms bridging across the wide pith-cavity at each node. Such a cast as that shown in fig. 100 is often referred to as _Calamites approximatus_ Brongn.; the length of the internodes and the periodic occurrence of branch-scars in the form of circular or oval depressions along a nodal line enable us to recognise the _Calamitina_ casts. Weiss[774] points out that in pith-casts of this form the branch-scars occur on the nodal constriction, and not immediately above the node as is the case on the surface of a typical _Calamitina_. This distinction is however of little or no value; the point of attachment of a branch may be above the nodal line, while on the pith-cast of the same stem the point of origin of the vascular bundles of the branch is on the nodal constriction[775]. The specimen shown in fig. 100 illustrates the appearance of a _Calamitina_ cast. There is a verticil of branch-scars on the lowest nodal constriction; on the right of the pith-cast the broad band of wood is faintly indicated by the smooth surface of the rock (_x_). Other examples demonstrating the existence of a broad woody cylinder in _Calamitina_ stems have been figured by Weiss[776] and other writers, and some good examples may be seen in the British Museum. [Illustration: FIG. 100. _Calamites_ (_Calamitina_) _approximatus_ Brongn. Lower Coal-Measures of Ayrshire. _x_, impression of the wood. (From a specimen in the collection of Mr R. Kidston.)] We have so far noticed the connection of certain forms of pith-casts (_e.g._ _Calamites approximatus_), and Asterophyllitean shoots with stems of the sub-genus _Calamitina_. As regards the strobili our knowledge is far from satisfactory. Stur[777] figures some fertile branches bearing long and narrow strobili, either _Palaeostachya_ or _Calamostachys_, in close association with _Calamitina_ stems, and Renault and Zeiller[778] give illustrations of the association of _Calamitina_ stems with large strobili of the _Macrostachya_ form.