Cycad

“ On adjacent flats and slopes grow survivals from one of the most ancient of all plants—a Cycad, that botanical paradox, combining some of the characteristics of the lie palm and of the pine with the appearance of a tree-fern, while being of distinctive order, which flourished during the age when the Iguanodon and the Polacanthus and other monstrous and ungainly reptiles roamed the land. ”

“ Cycad, sī′kad, n. an order allied to Coniferæ, but in appearance rather resembling ferns and palms.—adj. Cycadā′ceous. [Formed from Gr. kykas, an erroneous form of koikas, koiks, the doom-palm.]
Cyclamen, sik′lä-men, n. a genus of Primulaceæ, native to southern Europe. [Formed from Gr. kyklamis, -inos.]
Cycle, sī′kl, n. a period of time in which events happen in a certain order, and which constantly repeats itself: an imaginary circle or orbit in the heavens: a series of poems, prose romances, &c., centring round a figure or event—also Cy′clus: an abbreviation for bicycle and tricycle.—v.i. ”

“ An ascent to the summit of the Faro Island. . . . In making an ascent to the higher districts of this island, which attains an elevation of about 1900 feet above the sea, a little may be learned perhaps of the vertical distribution of the coast flora in this portion of the Solomon Group. The cycad (Cycas circinalis) grows most frequently just within the trees that immediately line the beach and may be often observed at all heights up to 400 feet above the sea, but it is not usually found at greater elevations. ”

“ The Lepidodendroids, Asterophyllites, and Annulariœ, of the Coal and Permian formations, have now apparently wholly disappeared: and the Triassic flora consists mainly of Ferns, Cycads, and Conifers, of which only the two Page 208 last need special notice. The Cycads (fig. 140) are true exogenous plants, which in general form and habit of growth present considerable
Fig. 140.—Zamia spiralis, a living Cycad. Australia. resemblance to young Palms, but which in reality are most nearly related to the Pines and Firs (Coniferœ) . ”

“ But few vestiges of the foliage of Cycads have been observed in the Wealden formation of England; one elegant leaf, however, of an undescribed species, was obtained some years since, from a sandstone quarry in Surrey, and is figured in my Geology of the South-east of England, p. 238; it is named in honour of my distinguished friend, M. Ad. Brongniart, Cycadites Brongniarti. The Wealden of the north of Germany is very rich in fossil Cycadeæ; my friend. Dr. Dunker, has figured and described twelve species in his admirable work on the organic remains of that formation. ”

“ Seeds albuminous, with one integument; the single embryo, usually bearing two partially fused cotyledons, is attached to a long tangled suspensor. Stems and roots increase in diameter by secondary thickening, the secondary wood being produced by one cambium or developed from successive cambium-rings.
The cycads constitute a homogeneous group of a few living members confined to tropical and sub-tropical regions. As a fairly typical and well-known example of the Cycadaceae, a species of the genus Cycas (e.g. C. circinalis, C. revoluta, &c.) ”

“ Though the cycads have a considerable range of organisation and of fructification, and though some points in reference to the latter might assign them a higher place, on the whole they seem to occupy a lower position than the conifers or the cordaiteæ of the Carboniferous. In the Carboniferous some of the fern-like leaves assigned to the genus Noeggerathia have been shown by Stur and Weiss to have been gymnosperms, probably allied to cycads, of which they may be regarded at least as precursors. ”

“ All the living species of Cycads are natives of warm countries, such as South America, the West Indies, Japan, Australia, Southern Asia, and South Africa. The remains of Cycads, as we have seen, are not known to occur in the Coal formation, or only to a very limited extent towards its close; nor are they known with certainty as occurring in Permian deposits. In the Triassic period, however, the remains of Cycads belonging to such genera as Pterophyllum (fig. 141, b) , Zamites, and Podozamites (fig. 141, c) , are sufficiently abundant to constitute quite a marked feature in the vegetation ”

“ The Cycas revoluta figured in Pl. 58 [54] possesses a peculiar interest in relation to both our fossil species, in consequence of its protruding a series of buds from the axillæ of many of the scales around its trunk. These buds explain analogous appearances at the axillae of many fossil scales on Cycadites megalophyllus, and Cycadites microphyllus (see Pl. 60, Fig. 1, and Pl. 61, Fig. 1,) and form an important point of agreement in the Physiology of the living and fossil Cycadeæ. ”

“ 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. E. horridus, the lamina is deeply lobed; and in a species of the Australian genus Macrozamia, M. heteromera, the narrow pinnae are dichotomously branched almost to the base (fig. 6) , and resemble the frond of some species of the fern Schizaea, or the fossil genus Baiera (Ginkgoales) . ”

“ One of the most important discoveries made during the latter part of the 19th century was that by Ikeno, a Japanese botanist, who first demonstrated the existence of motile male cells in the genus Cycas. Similar spermatozoids were observed in some species of Zamia by H. J. Webber, and more recent work enables us to assume that all cycads produce ciliated male gametes. Before following the growth of the pollen-grain after pollination, we will briefly describe the structure of a cycadean ovule. An ovule consists of a conical nucellus surrounded by a single integument. ”

“ In Mesozoic times cycadean plants were far more numerous and widely distributed than at the present time, and to adequately study the numerous fossil examples we need as thorough an acquaintance as possible with the comparatively small number of surviving genera and species. The less common and more isolated species of an existing family may often be of far greater importance to the palaeobotanist than the common and more typical forms. This importance of rare and little known types will be more fully illustrated in the chapters dealing with the Cycadaceæ and other plant groups. ”

“ The young leaves of Cycas consist of a straight rachis bearing numerous linear pinnae, traversed by a single midrib; the pinnae are circinately coiled like the leaf of a fern (fig. 3) . The male flower of Cycas conforms to the type of structure characteristic of the cycads, and consists of a long cone of numerous sporophylls bearing many oval pollen-sacs on their lower faces. The type described serves as a convenient representative of its class. There are eight other living genera, which may be classified as follows ”

“ More species of Cycadeæ occur among the fossils of this period, than are found living on the present surface of the earth. They form more than one-third of the total known fossil Flora of the Secondary formations; whilst of our actual vegetation, Cycadeæ are not one two-thousandth part.
The vegetation of the Third period approximated closely to that of the existing surface of the globe.
Among living families of plants, Sea-weeds, Ferns, Lycopodiaceæ, Equisetaceæ, Cycadeæ and Coniferæ, bear the nearest relation to the earliest forms of vegetation that have existed upon our planet. ”

“ The external appearance of Bennettitales justifies their early assignment to the Cycads, for the whole habit is Cycadean. The stems are either tuberous or cylindrical, and crowned by a rosette of large, fern-like leaves, giving to the cylindrical forms the appearance of tree ferns. The remarkable feature of Bennettitales, however, is the cone (strobilus) , whose structure is unique among Gymnosperms. These cones, instead of being solitary and terminal, in the midst of the rosette of leaves, as in most Cycads, are lateral on dwarf branches which arise in profusion from the stem. ”

“ During recent years a number of fossil (Carboniferous and Permian) plants have been very thoroughly investigated in the light of modern Stelar System of Cycadofilices. anatomical knowledge, and as a result it has become clear that in those times a large series of plants existed intermediate in structure between the modern ferns and the modern Gymnosperms (especially Cycads) , and to these the general name “Cycadofilices” has been applied. ”

“ 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. These concentric rings of secondary xylem and phloem (fig. 9) afford a characteristic cycadean feature. After the cambium has been active for some time producing secondary xylem and phloem, the latter consisting of sieve-tubes, phloem-parenchyma and frequently thick-walled fibres, a second cambium is developed in the pericycle ”

“ The Cycadophyte line is characterized by the retention of many of the fern-like features of the Cycadofilicales. In habit, in foliage, in stem structure, in sporangia, in reproductive habits, the features of Cycadofilicales were continued; so that the living Cycads, although relatively modern from the standpoint of history, are structurally the most primitive of living Gymnosperms, because they most resemble the historically ancient Cycadofilicales. ”

“ The stems of cycads are often described as unbranched; it is true that in comparison with conifers, in which the numerous branches, springing from the main stem, give a characteristic form to the tree, the tuberous or columnar stem of the Cycadaceae Stem and leaf. constitutes a striking distinguishing feature. Branching, however, occurs not infrequently: in Cycas the tall stem often produces several candelabra-like arms; in Zamia the main axis may break up near the base into several cylindrical branches; in species of Dioon (fig. 4) lateral branches are occasionally produced. ”

“ The leaves at once invite a comparison with ferns; the numerous long hairs which form a delicate woolly covering on young leaves recall the hairs of certain ferns, but agree more closely with the long filamentous hairs of recent cycads. The spermatozoids constitute the most striking link with both cycads and ferns. The structure of the seed, the presence of two neck-cells in the archegonia, the late development of the embryo, the partially-fused cotyledons and certain anatomical characters, are features common to Ginkgo and the cycads. ”

“ Dense forests of tree ferns throve in moist regions, and canebrakes of horsetails of modern type, but with stems reaching four inches in thickness, bordered the lagoons and marshes. Cycads were exceedingly abundant. These gymnosperms, related to the pines and spruces in structure and fruiting, but palmlike in their foliage, and uncoiling their long leaves after the manner of ferns, culminated in the Jurassic. From the view point of the botanist the Mesozoic is the Age of Cycads, and after this era they gradually decline to the small number of species now existing in tropical latitudes. ”

“ The cycads, offshoots of the ferns, through the strange group of trees known as the cycado-filices, spread through the woods.
The trilobites, to turn to animal life, all but disappeared, though one elegant example remained; the corals were changing; and the lamp-shells were dropping out. There were a few new species of fishes, but none of any great strength or capacity, and all preserving still the tail which is part of the backbone. ”

“ Fossil flowers of a type more like that of modern Cycads are few in number, and it is not by any means certain that all of those described as Cycadean flowers and seeds were borne by plants which should be included in the Cycadophyta; a few female flowers have been described from Rhaetic rocks of Scania and elsewhere under the name Zamiostrobus—these consist of an axis with slender pedicels or carpophylls given off at a wide angle and bearing two ovules at the distal end ”

“ In fact, finding similar fossil plants at places widely different in latitude, and hence in climate, is, in the present state of our knowledge, rather an argument against than for their having existed cotemporaneously. The Cycadeae, especially, whose fossil remains afford so much ground for geological speculations, are far from yielding such precise data as is supposed. Species of the order are found in Mexico, South Africa, Australia, and India, some inhabiting the hottest and dampest, and others the driest climates on the surface of the globe ”

“ The complicated girdle-like course is characteristic of the leaf-traces of most recent cycads, but in some cases, e.g. in Zamia floridana, the traces are described by Wieland in his recent monograph on American fossil cycads (Carnegie Institution Publications, 1906) as possessing a more direct course similar to that in Mesozoic genera. A leaf-trace, as it passes through the cortex, has a collateral structure, the protoxylem being situated at the inner edge of the xylem ”

“ If considered etymologically, it is merely a record of a past mistake, but it would be absurd to discard such a well-known name on the grounds that the genus is a Vascular Cryptogam and far removed from reeds. On the other hand, there often arise cases which present a real difficulty. The following example conveniently illustrates two distinct points of view as regards generic nomenclature. In 1875 Saporta described and figured a fragment of a fossil plant from the Jurassic beds of France as Cycadorachis armata [162] ”