Monday, January 14, 2013
The word “pod” is an old term that has a rather obscure origin, generally referring to something that contains something else. It’s a word that is commonly used to describe anything in the plant kingdom that contains seeds. In general, “pod” seems to be most commonly used for a fruit that is dry at maturity, and which eventually opens up (there are plenty of different ways) to let the seeds get out (plenty of ways for that, too). Sometimes you’ll hear people use the term “seedpod” for the same thing. For botanists, of course, such a word is not very precise, and since there are so many different architectures of dried fruits that open (or “dehisce”) to release seeds, a somewhat more complicated list of terms has developed. But then, botanists are fond of developing long lists of terms.
This plant produces a “pod”-like fruit that is technically what we call a follicle. You’ll see that a follicle splits open longitudinally along one line. Now a follicle is much like a bean, architecturally, except that a true bean splits open along two lines. (The word “bean” itself is a bit imprecise, as well, sometimes used for plants that aren’t in the bean family. Our Mystery Plant is obviously related to the familiar and common milkweeds, all of which have star-shaped flowers, and produce follicles as a fruit type.)
It’s a twining vine, native to the Southeast, found commonly in woods and thickets from Virginia to Mississippi, and through much of Florida. This species has about 100 close relatives in the same genus, most of which are tropical. Ours has handsome, dark green leaves which tend to be roundish and valentine-shaped. Two leaves occur at each node, and that’s where the small flowers will be found. The blossoms open up in the summer, in clusters at the nodes. Each of the 5 petals will be sort of purplish-brown, often with a green blotch.
But it’s the follicle that really stands out. It begins smooth and green, and during the summer, develops several prominent, raised angular ridges running the fruit’s length. As it ages, the fruit slowly changes from green to tan, about the same time that the vine starts to wither. At maturity, the dry follicles are about 5” long. I have several of these vines in my backyard now, and they are really putting on a show. The pods slowly split open, seeming to close up again when it’s rainy or damp. On a dry day, the seeds start to emerge and fall, and these produce the final touch to a magical show.
Each seed is about one-third of an inch long, and dark brown, or black, and featuring, on the widest portion, several toothy notches. The other end of the seed produces a fantastic spray of soft, white plumes. When the weather is right, the follicle spreads open a bit, and lets a few seeds at a time dribble out, instantly taken off by the slightest breeze. (You might recall an animated version of this in Disney’s 1940 film classic, Fantasia.)
[Answer: "Anglepod," Gonolobus suberosus]
John Nelson is the curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196.