Conifers are scantily represented by Callitris and Podocarpus, which is common to all three sub-regions; and Cycads by the endemic Encephalartos and Stangeria.
Encephalartos (South and Tropical Africa).
- Similar to Encephalartos except in the presence of a spinous projection from the swollen distal end of the carpels.
The South African Encephalartos frequently produces several branches.
The thick armour of petiole-bases enveloping the stem is a characteristic C y cad c an feature; in Cycas the alternation of scale-leaves and fronds is more clearly shown than in other cycads; in Encephalartos, Dioon, &e., From a photograph of a plant in the Peradeniya the persistent scale - leaf Gardens, Ceylon, by Professor R.
In rare cases the pinnae of cycads are lobed or branched: in Dioon spinulosum (Central America) the margin of the segments bears numerous spinous processes; in some species of Encephalartos, e.g.
3); in Encephalartos, Dioon, &c., both rachis and segments are straight; in Zamia the rachis is bent or slightly coiled, bearing straight pinnae.
Encephalartos) a considerable size, reaching a length of more than a foot.
Cases have been recorded (by Thiselton-Dyer in Encephalartos and by Wieland in Zamia) in which the short carpellary cone-scales exhibit a foliaceous form.
Encephalartos c, p roximal cell and Macrozamia).
Short and reticulately-pitted tracheal cells, similar to tracheids, often occur in the circummedullary region of cycadean stems. In an old stem of Cycas, Encephalartos or Macrozamia the secondary wood consists of several rather unevenly concentric zones, while in some other genera it forms a continuous mass as in conifers and normal dicotyledons.
The majority of Mesozoic stems agree in external appearance with those of recent species of Encephalartos, Macrozamia, and some other genera; the trunk is encased in a mass of persistent petiole-bases separated from one another by a dense felt or packing of scaly ramenta.
Mr Wieland has also described young bipinnate fronds, very like those of recent species of Zamia and Encephalartos, attached to a Bennettites stem, and exhibiting the vernation characters of many recent Cycads (fig.
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