The leaf-traces in an adult stem exhibit a striking feature in their indirect or girdle-like course to the leaves (fig. 396, H, _g_) and in the gradual change from an endarch (fig. 396, O) to an apparently mesarch structure (fig. 400) as they pass from the perimedullary zone to the petiole: except at the base of the petiole the vascular bundles of the frond-axis consist of (i) centripetally developed xylem with a median protoxylem and a much smaller amount of centrifugal xylem (fig. 400) separated by a few parenchymatous elements from the centripetal xylem, (ii) an external arc of protophloem and within this metaphloem and parenchyma[21]. In the slender petiole of _Bowenia_ there are a few collateral bundles arranged in the form of a circle or ellipse[22]; in _Cycas_ and some other genera the more numerous bundles form a pattern like an inverted U, and in some species of _Encephalartos_ the number is greater and the strands more irregularly scattered[23]. In the vegetative stems there is no centripetal xylem in the stele, but scattered centripetal tracheids occasionally occur internal to the protoxylem in the steles of the peduncles[24]. * * * * * =Cycadeae.= Megasporophylls each bearing 2–8 ovules, borne separately like foliage-leaves and not in strobili. Pinnae have a midrib but no lateral veins (figs. 384, 387, A). _Cycas_ (fig. 377). =Zamieae.= Both kinds of sporophylls form strobili. Pinnae have several dichotomously branched, more or less parallel veins. _Zamia_ (figs. 388–390), _Macrozamia_, _Encephalartos_ (figs. 379, 386, C), _Ceratozamia_, _Dioon_ (fig. 386, B), _Microcycas_. =Stangerieae.= Strobili as in Zamieae. Pinnae fern-like, numerous dichotomously branched lateral veins given off from a midrib. _Stangeria._ =Bowenieae.= Leaves bipinnate (fig. 391), strobili as in Zamieae. _Bowenia._