Species of Stigmaphyllon A. Jussieu (pronounced stig-meh-fil'-on) are woody vines (lianas) of the Malpighiaceae, a family that thrives in tropical and subtropical habitats. Certain members of this genus can be cultivated in Southern California as long as they are protected from freezing and receive enough summer heat to encourage flowering. And summer is when these plants are most enjoyable, because of their spectacular, bright yellow flowers.
Two species are happily growing at MEMBG. Stigmaphyllon littorale A. Jussieu, from coastal southern Brazil (littoral means along the coast), is easy to spot on the cyclone fence due south of the patio, next to our Tithonia diversifolia (see the winter 1999 newsletter) and entangled with several other lianas, including kiwifruit (Actinidia deliciosa). Stigmaphyllon.ciliatum (Lamarck) A. Jussieu, a widespread slender-stemmed climber of the Neotropics known as golden vine, is currently hiding on a trellis in the perennial garden, across the street from the Botany Building.
The ovate leaf of S. ciliatum is very distinctive among the plants in our collection. It has a pair of ear-like (auriculate) lobes at the bases, and along the leaf margin are prominent, glandular, hair-like (ciliate) teeth at the tips of major veins. The pointed leaf blade, usually four to seven centimeters in length, is glabrous--meaning that it bears no hairs at all--and may also have a bluish cast. Using a hand lens, you can observe a pair of green glands atop the petiole (i.e., situated next to the blade). Leaves are opposite, with each leaf pair spaced from the next by a slender internode at least ten centimeters in length.
The much larger leaf of S. littorale has a totally different look--several different looks, in fact--and a much softer feel. On certain leaves the blade is broadly ovate (up to 18 centimeter in length), while on others it is nearly triangular. Often the blade has a pair of noticeable lateral lobes on its lower portion. The pairs of petiolar glands on S. littorale can be seen even without a hand lens--but do take out your lens to look at the softer leaf blade underside! The softness in this family is caused by single-celled, T-shaped hairs, the so-called malpighian hairs. These hairs can be readily seen on the leaf underside along the midvein, where they are reddish in color, but on the adjacent green blade the malpighian hairs all tend to be translucent and very fine. Where leaves are large, up to twenty-five centimeters long with petiole, leaf arrangement is opposite, but along the long and unbranched stem one observes a transition to smaller leaves that are subopposite (i.e., not evenly paired) and then to alternate (i.e., with only one relatively small leaf occurring at each node). Sometimes the most slender shoot tips of this and the other species show twining, but typically the shoots are straight and pendant, or else they lie straight on the ground.
The reproductive features of this family are so bizarre that even a professional botanist needs to consult the manuals to interpret them. Each inflorescence grows from an axillary bud, commonly emerging at a right angle from the stem. At the top of that inflorescence stalk are small, highly modified bracts (leaves), each bearing a pair of green glands. To the best of my knowledge, these glands secrete sugar to attract ants, thereby distracting them from visiting the flowers. The pedicels of the flowers arise like an umbrella (they are nearly umbellate), although this is not the same type of inflorescence that one sees in the carrot family (which has true umbels).
The uniqueness of the flower is first observed in the bud. Where one might expect to observe five leaf-like sepals, instead one sees sepals that are highly reduced, each bearing a pair of green glands that have the appearance of an opened, bivalved clamshell. Remarkably, one of the five sepals lacks this pair of glands. These sepal glands must serve as nectaries. Petals in this genus, and elsewhere in Malpighiaceae, are described as being clawed (unguiculate)--there is a narrow stalk at the base, and thereafter the expanded portion is minutely fringed. Typically, each flower has five petals, but some may have only four, or five petals that may not all be the same size. Stigmaphyllon has three stigmas, and was so named (Greek stigma and phyllon, leaf) because each stigma bears a very conspicuous leafy portion next to the sticky stigmatic tip. These leafy stigmas tend to hide the three largest fertile stamens. Among the ten stamens present in the flower, often four are relatively short and have aborted or sterile anthers. Stigmaphyllon fruits have not been observed at MEMBG, but among the approximately eighty species, the ovary develops into a dry fruit, called a samara, with three chambers and three wings.
Flowers of S. ciliatum are three centimeters across, slightly wider than in the other species, but both species are a brilliant yellow when most flowers in a cluster are opened on the same day. Marcello Malpighi (1628 to 1694)--the famous pre-Linnean biologist at Bologna for whom this famili is a namesake--would have been quite happy to see such a spectacle.
ARTHUR C. GIBSON, Garden Director