The Middle Jurassic (Aalenian-Bajocian) shallow marine deposits of Bearreraig Bay, Skye, northwest Scotland, have yielded calcite-permineralized leaves of cycadophytes showing unusually well preserved anatomy. Morphological characters identify the leaves as Nilssonia cf. tenuinervis Seward (Cycadales), Otozamites mortonii sp. nov. (Bennettitales), a putative juvenile leaf showing imbricate, recurved pinnae, and Otozamites sp. Permineralized Jurassic cycadophytes occur in only four other localities worldwide; the better-known coeval adpression flora of Yorkshire lacks anatomical preservation. Past studies of fossil cycadophyte species have therefore emphasized morphology, whereas the Skye specimens reveal details of anatomy greatly exceeding published descriptions of similar species. The arrangement of vascular tissues in the rachis of Otozamites resembles that described for Ptilophyllum cutchense Morris (Bennettitales) from India. Stomata observed in the preserved cuticle of the Nilssonia leaf superficially resemble those of the extant cycad Macrozamia Miquel. Given the 180 million years separating these two genera, and the fragmentary preservation and equivocal phylogenetic position of Nilssonia, comparative interpretations remain tentative. Leaf characters have been little used in phylogenetic analyses, reflecting exaggerated fears of anatomical and morphological convergence; these characters therefore require particular attention when comparing fossil cycadophytes with their living relatives.

Polyxylic columnar stems covered by persistent leaf bases and found in sediments assignable to the Upper Cretaceous of Bajo de Santa Rosa, Río Negro Province, Argentina, are described as two new generic entities in the Cycadales. Anatomical characters are the basis for their being assigned to the Encephalartoideae of the Zamiaceae. Brunoa santarrosensis gen. et sp. nov. is characterized by the presence of polyxyly, cone domes, mucilage cavities, and uniseriate to triseriate araucaroid, scalariform, or bordered intervascular pitting. Worsdellia bonettiae gen. et sp. nov. has polyxyly, anastomosing medullary vascular bundles, centripetal xylem, mucilage canals, and concentric extraxylary bundles. Some characters (polyxyly, medullary vascular bundles, and cone domes) were used to determine the systematic position, while other characters (mucilage reservoirs and centripetal xylem) were used to establish the relationship between polyxylic and monoxylic forms.

The genus Cycas is revised for Vietnam. Twenty-four species are enumerated, nine of them described as new (C. aculeata, C. brachycantha, C. collina, C. condaoensis, C. pachypoda, C. dolichophylla, C. fugax, C. hoabinhensis, and C. tropophylla). Descriptions of two Chinese species known to occur close to the China-Vietnam border are also provided. A new combination is made for C. bifida (formerly C. rumphii var. bifida). The species are placed within an infrageneric classification previously outlined. Distribution of all taxa is mapped, and a key to species is provided. Illustrations are provided for new and poorly known taxa where adequate material has been available. Previous reports of C. circinalis and C. rumphii from Vietnam are discussed. Lectotypes are designated for C. balansae, C. chevalieri, and C. elongata, and a neotype is designated for C. pectinata.

There are three genera of cycads in Colombia: Cycas, with two introduced and unnaturalized species; the endemic genus Chigua, with two species; and Zamia, with 16 species, seven of which are endemic. Keys to all species are given, as well as complete descriptions, synonymy, types, exisiccatae, distributional data, and conservation status as used in the 1997 IUCN Red List of Threatened Plants. Floristically, Zamiaceae is represented in Colombia by four elements: a Chocó, southern Córdoba, and northeastern Antioquia element, with the endemic genus, Chigua, and six species of Zamia, Z. amplifolia, Z. disodon, Z. manicata, Z. roezlii, Z. chigua, and Z. obliqua, with the first two endemic to Colombia; a montane element in the northern Cordillera Occidental, with two endemic species, Z. montana and Z. wallisii; a Río Magdalena Valley element, with Z. muricata, Z. poeppigiana, and the endemic Z. encephalartoides; and an element east of the Andes and principally Amazonian, with four other species, Z. amazonum, Z. lecointei, Z. ulei, and the nearly endemic Z. hymenophyllidia.

The genus Ceratozamia has an extensive distribution that starts in northeastern Mexico and continues southward and southeastward into Guatemala, Belize, and Honduras. Over this extensive distributional range Ceratozamia is found in numerous disjunct populations. These populations are never very widespread and are often restricted to a single mountain or canyon. Because of the restricted range of these populations, and the lack of genetic exchange between them, many of them have evolved into easily identifiable groups. At the present time there are 16 validly published species of Ceratozamia, with several more possible new species under investigation.

The Mexican cycad Dioon edule with its two varieties, edule and angustifolium, range from the states of Tamaulipas and Nuevo León in the north to the state of Veracruz in the south. The variety angustifolium is restricted to the northern portions of the range, while the variety edule is from the southernmost distribution in central Veracruz. Between the two varieties of Dioon edule there are a number of disjunct colonies that exhibit variations that are undoubtedly the result of an extended period of genetic isolation. These colonies display variation in the maximum size of their stems, morphology and color of leaves and leaflets, distinctions in both male and female cones, color of the sarcotesta, and size and shape of the sclerotesta. These differences are maintained even when specimens are grown in cultivation under identical conditions. Critical investigations of these colonies may ultimately disclose the need for additional species descriptions.

A group of eight species of Encephalartos, comprising E. altensteinii, E. arenarius, E. horridus, E. latifrons, E. lehmannii, E. longifolius, E. princeps, and E. trispinosus, from the Eastern Cape Province of South Africa, was studied by analysis of iso-enzymes, ribosome DNA, and ITS 1 and 2 genes. The reason for this investigation was that the morphology of the vegetative and reproductive parts, though very distinctive in this geographical region, do not correlate, and it was hoped that molecular data would elucidate evolutionary relationships. The three sets of molecular data were found to agree to a remarkable degree. It was concluded that the vegetative morphology was misleading but that the cone characteristics agree with molecular data and provide insight into the interrelationships of these species. Thus, E. princeps was concluded to be relatively remotely related to the vegetatively similar E. lehmannii, and E. arenarius is not at all close to E. latifrons even though the two species are easy to confuse when not in cone.

The results of a pilot DNA sequencing study of cycads conducted at the new molecular systematics laboratory at Fairchild Tropical Garden are presented and assessed with reference to previous phylogenetic analyses and classification schemes based on morphology and anatomy. Two DNA regions were sequenced and analyzed for variation, an intron in the trnL gene in the chloroplast genome (trnL intron) and the internal transcribed spacer region between the 5.8S and 26S ribosomal DNA subunits (ITS2). The trnL intron proved to be relatively conservative among cycad genera, while the ITS2 region contained higher levels of variation. Parsimony analysis of the sequences suggests a number of relationships, some of which were inferred by previous morphological studies, some of which are new. The sequences of Cycas are the most divergent among cycads, suggesting the longest isolation. Dioon is relatively isolated from the other genera and contains two major clades. Stangeria does not appear closely related to Bowenia but does seem to have a weak affinity with Zamia and Microcycas. Lepidozamia is more closely related to Encephalartos than to Macrozamia. Sequence variation among the species of Ceratozamia is low. Microcycas and Zamia are closely related.

A list of the 305 currently recognized cycad species is given, along with citations of the original place of publication and the location of type specimens when known. Included in the list are currently recognized infraspecific taxa, brief geographical ranges, and a partial list of synonyms for each taxon.

We describe the spatial distribution, population structure, and fecundity of Ceratozamia matudai in two populations in the El Triunfo Biosphere Reserve, in Chiapas, Mexico. Three random plots of 20 × 20 m were laid out in a cypress forest habitat of the cycad and six plots in a cloud forest habitat on Mount Ovando. The aggregated spatial pattern of C. matudai showed a clumped local distribution on shallow soils on steep slopes. Individuals between the sites showed differences in leaf production, trunk diameter, height, and growth pattern. A population structure with an inverse “J” curve was obtained in both sites. Emergence of male and female cones appears to be synchronous in both populations, with a predominance of male cones recorded.