of vascular tissue for separate bundles and to some extent in the disposition of the bundles. The two types of petiole _Kalymma_ and _Calamopteris_, as Scott and Jeffrey state, are very closely allied. Dawson and Penhallow[498] have also described _Kalymma grandis_ from Kentucky but they, like Unger, mistook the hypodermal stereome for an outer zone of vascular bundles. The petioles from Germany and North America included under the name _Kalymma grandis_, though too similar to be referred to different species, no doubt represent petioles of stems which are unquestionably distinct types: as in the case of _Myeloxylon_ in its relation to the genus _Medullosa_, _Kalymma_ stands for several closely allied forms of petioles belonging to several species of _Calamopitys_. [Illustration: Fig. 456. _Kalymma grandis._ (From a section in the possession of Prof. Bower; × 4.)] =Eristophyton.= Zalessky. _Eristophyton fasciculare_ (Scott). The generic name _Eristophyton_[499] was proposed by Zalessky[500] for two incomplete stems of Lower Carboniferous age provisionally[501] referred by Scott to _Araucarioxylon_ and subsequently to _Calamopitys_[502]. The species _E. fasciculare_ was founded on material obtained by Dr Kidston from the Lower Carboniferous of Dumbarton, Scotland, and on a specimen in the Williamson collection from Northumberland. There is a small pith of parenchyma, 2–3 mm. in diameter, with eight strands of primary xylem of varying diameter (fig. 457) and in each a single protoxylem-group. The primary xylem elements are considerably larger than the secondary tracheids. These xylem-bundles are leaf-traces and their disposition points to a phyllotaxis of ⅖. The traces attain their maximum size when about to pass out through the secondary xylem. The tracheids are reticulate and scalariform while some have an intermediate type of pitting. A leaf-trace on reaching the pith gradually moves further from the xylem-cylinder and may be separated from it by 2–6 layers of parenchyma: as it passes down the pith the protoxylem strand assumes an almost endarch position consequent on the reduction of the centripetal xylem. In Scott’s words, ‘each circummedullary strand branches at regular intervals; the one branch, that on the anodic side [turned towards the course of the genetic spiral], becomes the leaf-trace and passes out, while the other continues its course up the stem as a reparatory strand, until the next leaf of the orthostichy has to be supplied[503].’ The secondary xylem consists almost entirely of tracheids with 3–4 rows of pits on the radial walls and medullary rays usually one cell broad varying in depth from 1 or 2 to 16 or more cells. A characteristic feature of the secondary xylem is the occurrence on its inner face of numerous short and broad tracheae similar to the still larger tracheae in the primary stele of _Megaloxylon_[504]. Nothing is known as to the behaviour of the