The Pandaniflorae, as here treated, are a group of monocots comprising two families: the Pandanaceae (screw-"pines") and the Cyclanthaceae (Panama hat plants). The inclusion of these two families together in a separate group is a relatively new idea based on the analysis of genetic sequences in the chloroplast (Duvall et al. 1993), but it is by no means an unusual one. There has been general agreement that the Cyclanthaceae and Pandanaceae are closely related, and they have usually been considered close relatives of the palms, which they resemble. This has been borne out by molecular data, though it is now believed that the palms are not part of the Pandaniflorae clade.
The Cyclanthaceae are a neotropical family, while the Pandanaceae are paleotropical. That is, the cyclanths are found in the New World tropics, while the pandanes are restricted to the Old World tropics. Distributions like this are not uncommon among the groups of flowering plants, and are usually interpreted to mean that the ancestors of both clades originated in the latter part of the Mesozoic on the great southern continent of Gondwanaland, and their descendants became separated as this continent broke into South America, Africa, Australia, Antarctica, and India.
Whether this is the case for the Pandaniflorae is unknown, however, since their fossil record is rather poor. There are Viracarpon fossil fruits from the Eocene of India which have been suggested as belonging to the Pandanaceae, but these have not been followed up by further investigation. There is also Maastrichtian (Late Cretaceous) pollen from North America which has been described as perhaps belonging to the pandanes, but more recent evidence shows that pollen of this kind comes from a floating aroid (Stockey et al. 1997). The fossil leaf Pandanites of North America was so names because of its superficial resemblance to Pandanus leaves, but there are no characters in the fossil specific to pandanes -- the fossil could come from an agave or or large monocot. Though there is no reported fossil record for the Cyclanthaceae, it is quite possible that some of the fossil leaves described as belonging to palms may actually belong to this group.
Pandanus : The pictures above show why Pandanus is called "screw-pine". The image on the left is a close-up of the flying buttresses which support the tree; note the spiral pattern in the bark. The image on the right shows a stand of pandane trees; note the tiny person at the bottom of the picture.
Both the Cyclanthaceae and Pandanaceae have a strong resemblance to palms, though the architecture of each group resembles the palms in different ways. In the pandanes, there is usually a central trunk supported by massive buttress roots, and the spiny strap-like leaves are clustered at the tips of the branches. You can see this in the pictures above. Some species of pandane grow as short shrubs, and these may be grown as greenhouse or indoor plants. All pandanes however, have a growing tip that spirals as it grows, giving their stems the appearance of a screw, and hence the common name of the group.
By contrast, the cyclanths are rarely tree-like. They creep along the floor of the rainforest by means of stems growing horizontally underground, or along the surface of surrounding rocks and vegetation. It is the large and divided leaves that comprise the majority of the plant. Like palms, the leaves of cyclanths are folded as a paper fan, and may be divided into two or more blades.
Both families have large and often complicated inflorescences. An inflorescence is a cluster of flowers on a single stalk, and in these groups those flowers produce either pollen or seeds, but not both. Such a division of labor between flowers which produce pollen (from which sperm comes) and seeds encourages diversity in the next generation. In cyclanths, the pollen and seed flowers are arranged together in the same inflorescence, while a pandane tree will produce only one kind of flower or the other. When mature, the seed flowers develop into clusters of fleshy fruits.
Carludovica : A representative member of the Cyclanthaceae. On the left is a closeup look at a flowering stalk. On the right is a full-view of a small plant growing in the understory of a rainforest; note the resemblance to a palm.
Pandanes have played an important part in the economy of Polynesians and of the aborigines of Australia. The fibers in the leaves are tough, and may be used for textiles. The trees themselves are ecologically important in the Pacific and Old World tropics, where they provide habitat for epiphytes and nesting birds. The leaves of Cyclanthus palmatus have long been used in tropical America for weaving hats, from which the group gets its common name.
The living Pandaniflorae may be divided into the following families:
For more information about the Pandaniflorae, try the DELTA descriptions of the Pandanaceae, and Cyclanthaceae, or visit Texas A&M for lists of more technical information.
Or try Roger Eriksson's Systematics of the Cyclanthaceae. For pictures on the web, try the Missouri Botanical Garden's pictures of Pandanaceae flowers, or the Panadanaceae images at Texas A&M.
Or read about how Polynesians made use of lauhala (Pandanus leaves) for things such as sail making.
Sources:
C. P. Daghlian. 1981. A review of the fossil record of monocotyledons. Botanical Review 47(4): 517-555.
M. R. Duvall, et al., 1993. Phylogenetic hypotheses for the monocotyledons constructed from rbcL sequence data. Ann. Missouri Bot. Gard. 80: 607-619.
J. Muller. 1981. Fossil pollen records of extant angiosperms. Botanical Review 47: 1-146.
R. A. Stockey, G. L. Hoffman, & G. W. Rothwell. 1997. The fossil monocot Limnobiophyllum scutatum; resolving the phylogeny of Lemnaceae. American Journal of Botany 84(3):355-368.
Benjamin C. Stone. 1968. Morphological studies in Pandanaceae. I. Staminodia and pistillodia of Pandanus and their hypothetical significance. Phytomorphology 18(4): 498-509.
