This is a dioecious genus.
Etymology: Genus name, honors the 19th century German industralist, Jacques Louis Fréderic Ravené.
Ravenea In Madagascar By Dr. Henk Beentje
Ravenea is becoming popular again. In the latter part of the 19th century, R. hildebrandtii was much sought after for the drawing room; nowadays this species is very rare in cultivation, and our more climatically advantaged members proudly grow their R. rivularis. Several entrepreneurs are trying to obtain seed of the rare R. xerophila, which would thrive in rather arid climes. However, the bulk of the genus is still unknown to the palmeteers' world at large, and that is sad, because there are some beautiful species as well as some very interesting ones. The genus is restricted, in the wild, to Madagascar and the Comoro Islands; your editors have described the Comoro species in this journal (Dransfield and Uhl 1986) and in a recent article I have described the amazing aquatic Ravenea (Beentje 1993). In 1995, John Dransfield and I hope to publish "Palms of Madagascar" which will contain full descriptions of the species, identification keys, and drawings as well as photographs. In this article I'd like to give you an overview of the genus.
One of the more amazing things about Ravenea is the sheer diversity of the species. Their habit ranges over a wide spectrum, including small undergrowth palms (R. hildebrandtii), short and squat palms (R. louvelii), slender middle-sized trees (R. madagascariensis) and forest canopy giants with bulging trunks (R. robustior); habitats include dense lowland rain forest where the palm collects litter (R. albicans), littoral and montane forests (R. sambiranensis), ravines in rather dry areas (R. glauca), river banks in dry areas (R. rivularis) and hilltops in arid areas (R. xerophila).
In fact, the genus itself is a member of a closely knit group of genera, the tribe Ceroxyleae, from a diversity of continents. There is Oraniopsis from Queensland, Australia; both other members of the tribe grow in South America; there is Juania from 'Robinson Crusoe' (Juan Fernandez) Island, and the Andean wax palms, Ceroxylon, occur in the high mountains of the Andes.
There used to be a fifth member of the tribe, Louvelia, also from Madagascar; however, John Dransfield and I have re-found the two most mysterious Louvelia species, and some intermediates, and it has turned out that there are no true differences between Ravenea and Louvelia. The two genera form a continuum, with the species at the opposite ends of the spectrum very different; if just the extremes were known, you would certainly put them in different genera. But, if you look at the other species, you can form a chain, of which the links are formed by species which are quite close to each other-and so you can link the extremes, making this a single genus. Between the bulk of the genus Ravenea and the other genera of this group, however, there are differences which cannot be bridged by intermediates. And so it goes.
History of the Genus
One of the main difficulties in the early days of Ravenea taxonomy was the scarcity of collections and the sex question. Species were described based on one or two collections, and often from very scrappy ones; this was the reason why early keys to the species were based on the strangest of characters, such as the keel of the leaf rachis, or little black hairs on the petiole (probably a fungus). By 1945, when the Flora of Madagascar and the Comoros was published (Jumelle and Perrier 1945), nine species had been recognized in Ravenea and three in Louvelia, and all but one of these have survived my critical revision (Beentje 1994). Several new species have come to light since 1945. Dransfield and Uhl (1986) described the imposing Ravenea moorei from the Comoro Islands. John Dransfield found a new species during his field work in the late 1980's, which was intermediate between Ravenea and Louvelia. During my own field work in Madagascar in 1991 -1993, three more new species came to light, one of which was described in this journal (Beentje 1993). The main difficulty during my revision of the genus was the distinction of taxa which are quite close to each other, such as R. madagascariensis, R. latisecta, and R. sambiranensis. In the field these seemed quite distinct, but the types, the specimens on which the first descriptions were based, were scrappy, or even completely missing-such as the type of R. latisecta - in which case I had to go by the rather hazy published description. The fact that this is a dioecious genus, with male and female trees, made the identification of scrappy specimens difficult, and so was the linking of the females with the appropriate males. So some mysteries remain; probably a good thing, as mysteries are the spice of life! Dr. Henk Beentje Royal Botanic Gardens, Kew (Read on below), edric.
The following 26 pages are in this category, out of 26 total.