The natural order Cycadaceæ is not so largely represented at the present day as it was during the Mesozoic epoch. Among the genera of the present day are Cycas (Fig. 74), Zamia, Macrozamia, Encephalartos (Fig. 75), Dion, Stangeria, etc. They are small palm-like trees or shrubs, with unbranched stems, occasionally dichotomous, marked with leaf-scars, and having large medullary rays along with pitted woody tissue. The leaves are pinnate, except in Bowenia, which has a bipinnate leaf. Males in cones. Females consisting of naked ovules on the edges of altered leaves, or on the inferior surface of the peltate apex of scales.[18]
[Flora of the Trias and Lias Epochs.]
Fig. 74. Fig. 75.
Fig. 74. Cycas revoluta, one of the false Sago-plants found in Japan.
Fig. 75. Encephalartos (Zamia) pungens, another starch-yielding Cycad.
In this reign the Acrogenous species are less numerous; the Gymnosperms almost equal them in number, and ordinarily surpass them in frequency. There are two periods in this reign, one in which Coniferæ predominate, while Cycadaceæ scarcely appear; and another in which the latter family preponderates as regards the number of species, and the frequency and variety of generic forms. Cycadaceæ occupied a more important place in the ancient than in the present vegetable world. They extend more or less from the Trias formation up to the Tertiary. They are rare in the Grès bigarré or lower strata of the Triassic system. They attain their maximum in the Lias and Oolite, in each of which upwards of 40 species have been enumerated, and they disappear in the Tertiary formations. Schimper describes 13 genera of fossil Zamiæ, and about 20 Cycadeæ. He thinks that Trigonocarpum (15 species), Rhabdocarpum (24 species), Cardiocarpum (21 species), and Carpolithes (9 species), are all fruits of Cycadeæ. Many supposed fossil Cycads are looked upon by Carruthers as Coniferæ. Zamia macrocephala, or Zamites macrocephalus, or Zamiostrobus macrocephalus, is called by him Pinites macrocephalus; Zamia ovata, or Zamites ovatus, or Zamiostrobus ovatus, is Pinites ovatus; Zamia Sussexiensis is Pinites Sussexiensis. Among other species of Pinites noticed by Carruthers are Pinites oblongus, P. Benstedi, P. Dunkeri, P. Mantellii, P. patens, P. Fittoni, P. elongatus. It is important to notice that in an existing Cycad called Stangeria paradoxa the veins of the pinnæ rise from a true midrib and fork, characters which render untenable the distinction usually relied upon between the foliage of Ferns and Cycads.
Fig. 76.