Species of the Week: Jack in the Pulpit

Species of the Week
Number 39 -- May 7, 2007

In the Species of the Week feature of the Wildwood Web we took a close look at one of the species that lives in Wildwood. To see the earlier featured species check the Species of the Week archives.

Jack-in-the-Pulpit

Arisaema triphyllum

Jack-in the-pulpits are surely one of the oddest flowering plants in Wildwood. What most people think of as the flower is really an inflorescence, a cluster of flowers. However, the actual flowers in the cluster are hidden away inside the "flower" that we admire. Few people have actually seen the flowers. Instead we see a spongy, cylindrical structure, the "Jack," inside a leaf-like structure that is rolled into a deep cup with an overhanging roof, the "pulpit." The whole ensemble does somewhat resemble a diminutive minister in an old-fashioned high-church pulpit. Botanist call the minister a spadix, while his pulpit is the spathe. In the case of Jack-in-the-pulpits, neither of these is a flower, or part of a flower. Instead, the true flowers are tiny and located at the very base of the spadix inside the spathe.

		This odd floral structure has evolved in the Araceae or Arum Family, and nearly all members of the family show variations on this structure, with a leafy spathe partly or almost completely surrounding a cylindrical or spherical spadix from which the tiny flowers emerge. This is a family of mostly tropical species. Only a few are found in North America, and many of those are rare. No other member of this family occurs in Wildwood, and the only other member common in our area is the skunk cabbage, which occurs in very wet areas that are more acidic than Wildwood. However, most people are familiar with this family because it contains many of our most common houseplants, including philodendrons, Swiss-cheese plants (Monstera), dumbcane (Dieffenbachia), caladiums, and peace-lilies (Spathiphyllum). The calla lilies of gardeners are also in this family. The flowers of calla lilies and peace-lilies clearly demonstrate the spathe and spadix structure of the inflorescence, but most of these plants rarely flower in cultivation, and are grown for their foliage. Jack-in-the-pulpits are perennials that pass the winter underground as corms. In the spring, they send up a shoot, as at left, which unfolds one or two leaves and a "flower" The leaves are divided into three leaflets, from which we get the species name, triphyllum, meaning "three-leaved." The spathe or pulpit is green, with white, brown or purple stripes. The spadix or minister is usually a pale cream inside green and white spathes, and purple inside purple-striped spathes. The leaf stalks of plants with purplish flowers are often purple-spotted.

These plants are also unusual in that each plant has a particular sex. In most plants, each flower contains both male and female parts. However, in a few plants--Jack-in-the-pulpits being one-- each plant has either male or female flowers. How can you tell the difference? If you look carefully at the spathe you will see that it is not a perfect cup, the front is closed up merely by the two sides of the spathe overlapping. Carefully open up the front and look inside. If it is a male plant you will see tiny thread-like yellow to brown anthers at the base of the spadix. If it is a female, you will see a cluster of tiny green berries, the female flowers. Once the male plant has finished blooming, the floral structure will wither and die. If the female flowers are pollinated, however, the flower will persist throughout the summer, although in a collapsed, inconspicuous state. The tiny green berries that are the female flowers will grow large as one to three seeds develop and the plant pumps food into the pulp around them. When the seeds are ready in the autumn, the berries turn brilliant red, as seen at right, and are eaten by birds. The pulp provides a little reward to the birds for carrying the seeds somewhere else and planting them, along with a bit of fertilizer, when they relieve themselves.

		One might think that having male and female flowers widely separated on different plants and hidden away deep inside a nondescript green tube is not a good plan for ensuring pollination. Jack-in-the-pulpits manage, however. The cylindrical spadix is not there just for decoration. This organ has a job--to produce an odor of mushroom which attracts tiny insects known as fungus flies. They fly into the tube of the spathe looking for fungi on which to lay their eggs. Once inside they become confused, because the hood of the spathe blocks the light from above, while the lowest part of the spathe is paler, and hence lets in more light. The flies, being attracted to the light move downward to the flowers and either pick up or drop off pollen, depending on the kind of flowers inside. Although each Jack-in-the-pulpit plant is a particular sex, it may not stay that sex very long. Each autumn, as the flower and leaf buds form for the next spring, the plant decides either to be male or female, and may thus change it's sex every year. On what basis does the plant decide its sex? Consider that being male is a piece of cake compared to being female. While the males must produce a batch of pollen in the spring, they then let their flowers wither and spend the summer soaking up rays and storing food in their underground corms. The females, on the other hand must make seeds, pack them with nutrients for the baby plants, and then coat them with nutritious berries to bribe birds into dispersing them. Clearly being female takes a lot more resources.

So, in the autumn, the plant somehow senses how much food has been stored away in the corm. If it's been a good year and the corm is packed with nutrients, the plant produces a bud for female flowers and, usually, for two leaves, to make more sugars by photosynthesis. If the year has not been that good, and the corm is a bit low on resources, the plant will make a bud for male flowers and one leaf. Thus, you can easily tell the sex of the plant without having to peer in on the hidden flowers. If there are two leaves, as in the lady at right, it's female. If there's but one leaf, as in the fellow in the picture above left, it's male. Although the books I've consulted suggest that the plants may occasionally produce the wrong number of leaves, or even make three leaves, whenever I've checked, two leaved plants have always been female, and one-leaved plants have always been male. I have heard that if a plant coming up female has its sprout chopped off, it will produce another sprout, but this time male, since it has lost the energy that went into the first sprout. If it's been a really bad year, and the corm is feeling stunted, it can forego the flower altogether and produce only a bud for a single leaf, as seen in the two plants below. Very young plants, which have not yet had a chance to grow a good-sized corm, also produce only a leaf.

		Producing but a single leaf may seem risky; what if something eats your leaf? Few animals or insects, however, eat the leaves of Jack-in-the-pulpits, which are poisonous. The corm, too, is poisonous. Nibbling it produces an intense burning sensation in the mouth, and the lips and tongue may subsequently swell so badly as to impair breathing. Leaves and corms both contain microscopic crystals of calcium oxalate, which have often been blamed for the poisonous qualities of the plant. However, prolonged cooking or thorough drying renders the plant non-poisonous while leaving the crystals intact, so it is now assumed that some poisonous chemical associated with the crystals is destroyed by heating or drying. Another name for the plant is Indian turnip, and it has been assumed that Native Americans used the plant as a root vegetable, but only after either prolonged baking or thorough drying. Donald and Lillian Stokes in Enjoying Wildflowers (Little Brown & Co., 1984) suggest that eating the plant would not have been worth the trouble, except in starvation years. On the other hand, edible plant books recommend grinding the corms, after thorough drying, to produce a fine flour, and eating the sliced, but thoroughly dried corms, like potato chips. Given the dangers, I would recommend merely admiring the plant and eating only foods that don't have to be treated extensively to make them non-poisonous.

In the nineteenth century, preparations of the plant were used as an expectorant and to treat asthma, rheumatism and whooping cough. They worked by creating irritation. The plant had to be partially dried for this purpose, since the completely dried plant would be non-poisonous and hence useless. On the other hand, an insufficiently dried specimen could be deadly. Supposedly the preparations could also be used as a form of birth control by causing temporary sterility, but I have serious doubts about their effectiveness.

Jack-in-the-pulpits like moist to dry deciduous woodlands, bottomlands, swamps and bogs from Nova Scotia south to Florida and west to Manitoba and Texas. In Wildwood it grows predominately on the western slope of the Park, close to Connelly's Run. The genus Arisaema contains some 170 species, mostly in temperate Asia, but also in North America and Africa. Only two species have made it to North America. Jack-in-the-pulpit is one species. The other, Arisaema dracontium, the green dragon, is rare, but is known from Virginia. In the past, Jack-in-the-pulpits were divided into as many as five separate species, based on differences in size, the shape of the leaves, fluting on the spathe, and the moistness of their preferred habitat. However, the "species" tended to blend into one another, so most botanists now consider them a single, variable species. The genus name Arisaema comes from the Greek aris, an unknown plant, probably in the Arum Family, mentioned by Pliny, plus haema, meaning "blood" and referring to the red spots found on the leaves of some species.

As I said above, few people have seen the the true flowers of Jack-in-the pulpits, since it is first necessary to peel open the spathe and peer inside. Even then, a hand lens is recommended. The pictures here show individual flowers photographed through a microscope At the left is a single male flower, with more male flowers in the background. At right above is a single female flower. The flowers were first rendered transparent by chemical treatment and then photographed using a type of microscopy called polarization microscopy which causes the cell walls of the plant cells to glow. Crystals also glow, and crystals of calcium oxalate can be seen lining the outer walls of the female flower, although no crystals can be seen in the male flower. The size of the flowers can be judged by the scale bars, which are 100 micrometers or 0.1 millimeter long.

GGC