Predatory Pitcher Plants

 

Kids like creepy crawly things.  Turtles, spiders, snakes, and frogs by the hundreds are smuggled in pockets or damp cardboard boxes into otherwise tidy if well-worn and slightly over decorated middleclass homes every year.  And perhaps, for every ten or so frogs that are secreted from garden to kitchen, one Venus Flytrap makes its way from garden center or nursery to a window sill in a home.  Kids, and kids at heart are fascinated by the snapping prickly maw of these strange plants.  They have been featured in films more often than their fictional cousins, the killer tomato and space-faring body snatcher pods. It is probably the one specific plant that more people recognize than any other.  Yet few are familiar with its much more common and varied cousins, the pitcher plants.  Flytraps are lucky to catch anything as large as a wasp, while pitcher plants are capable of capturing large tropical insects, and some can capture birds and occasionally small mammals. Just as thousands of other dinosaurs reside in the shadow of the famed Tyrannosaurus Rex, pitcher plants lurk in the shadow of their fly trapping cousin, with just as much capacity to capture the imagination, if given a chance. 

A stunning variety of pitcher plants forms are found across five continents, in warm tropical and subtropical regions of the world.  They use stealth, rather than speed or brute force, to outwit their prey.  They combine cleverly formed leaves with vivid color patterns normally only found in flowers and the irresistible lure of nectar.  Unsuspecting insects behave as if they’ve found a blossom, and take the bait.  But the promise of a meal in exchange for pollination, which many of the victims instinctively expect, is merely a ploy.  The “flower” is a trap; a waxy slide with formidable restraints barring retreat from the watery grave that waits below.   Bees, ants, and other insects detect nothing out of the ordinary until it is too late.  While lacking the drama of a pouncing lion or a lunging crocodile, or even a snapping flytrap, they are equally skillful at capturing prey. 

Pitchers serve a dual function.  Once an insect is captured, they function like a digestive organ.  In some pitcher plants, the pitcher produces enzymes that break down the body of the prey.  In others, the plant relies on a symbiotic relationship with bacteria that assist with the digestion.  In all cases, the pitcher then absorbs the nutrients and serves as a watery grave for indigestible exoskeletal remains.  Older pitchers are periodically shed as their capacity to digest insects gradually decreases.  In essence, pitcher plants are able to produce an endless supply of mouths and stomachs!

While most other plants have had to solve more basic challenges of collecting enough sunshine to generate and store energy for growth, to extract and retain water in dry climate, or to find clever ways to entice pollinators and seed dispersers, pitcher plants have had the added challenge of finding sufficient nutrients where frequent rains leach out nitrogen and trace elements.  Somehow, the plants realized that rich sources of these necessities of life buzzed and hopped and crawled all over them, and so they quietly set about the task of availing themselves of this alternate food source.  Pieces of this evolutionary puzzle reveal themselves in the various forms that living pitcher plants assume around the globe. 

 

South America’s Primitive Sun Pitchers

 

Afternoon rains fall in torrential sheets over a rocky bowl-shaped depression high atop a flat-topped tropical mountain.  Stunted trees of various shapes and sizes cling to the edge of ponds and streams forming dwarf mini-forests.  Vast tangles of green stretch as far as the eye can see.  Everything seems vaguely familiar, yet miniaturized and primitive.  Many plants have tough bluish leaves.  Others have vivid yellow- or red-green leaves that look durable but are actually as brittle as crisp lettuce.  As a strong wind sweeps the plateau, vast mats of vase-shaped pitchers bob and sway against the pouring rain that comes everyday.  Excess water flows out of barely discernable slits in the front of each vase, which are cleverly constructed drains that help the plant cope with precisely this type of weather.  The rain stirs a thick soup that fills the vessel below its constricted waist, and insect legs and mandibles are loosened from the recesses to dance and swirl until the storm passes. 

 

One group of plants from South America retains a form that is likely the ancestral form of at least one line of pitcher plants.  Native to high mountain plateaus, called tepuis, in Venezuela, Guyana, and Brazil, these represent an ancient and primitive pitcher plant form.  The trap is basically a broad leaf that has curled lengthwise onto itself.  The genus Heliamphora is widely believed to represent the most primitive of the pitcher plants living today.  Still rare in cultivation, the various species are sometimes collectively referred to by their common name of “sun pitchers.”  The simplicity of this vase-like design might be overlooked were it not for the fact that even these primitive plants recognize and address the need to lure prey, rather than merely wait for meals to fall from the sky.  Heliamphora are one of three types of related pitcher plants that live in the Western hemisphere.  They reside primarily on the tepuis that dot the north eastern portion of the continent.  Tropical rains have eroded away much of these tall islands.  As they’ve been separated by the elements, a number of species have emerged to fill local niches.  The number of species is believed to be between 8 and 10, with plant forms ranging from very small clusters of hourglass shaped pitchers standing just a few centimeters high but forming vast mats in boggy locations (H. minor), to rosettes of wide mouthed vase-shaped pitchers that can reach or exceed half a meter (H. ionasi), and strange shaggy shrubs that can grow to nearly two meters high covered with tall narrow maroon funnels crowding otherworldly highland meadows (H. tatei).  Of the pitcher plants found in the new world, the Heliamphora have the most attractive and accessible flowers.  Each plant produces an average of 2 to 5 tear-drop shaped pink to white flowers that gradually open to a star shape that lasts for as long as six to eight weeks.  Only the flowers of the cobra lily of the American Pacific Northwest bear any resemblance to the blossoms of the sun pitcher.

All sun pitchers share the same basic form – a funnel shaped leaf lined with downward pointing hairs, yellow-green to red or dark purple in color, topped with a small nectar-producing cap, and cleverly equipped with a small drain partway down the pitcher to help them cope with heavy rains without losing their lunch in the process.  Most reside at high altitudes (above 2000 meters) and are exposed to cool, wet temperatures, fog, and high doses of ultraviolet radiation.  The leaves are thin and crisp, and very easy to break.  Most are actually quite easy to grow in that once you establish acceptable conditions, there’s no need to adjust for seasonal variations.  Basically, they require lots of water, high humidity, cool temperatures, and high light (ideal under fluorescent lighting).  A couple of species have migrated down into the tropical rainforests that nestle up to the tepuis and cling to the rivers and streams that tumble or trickle down their steep slopes.  But were it not for the fact that they reside in regions that were largely inaccessible before the invention of the helicopter, these living carnivorous plant fossils might have been lost long ago.  While no one has managed to locate the dinosaurs that Sir Arthur Conan Doyle suggested might live in this region, scientists and hobbyists continue to find strange new plants with each visit to this “Lost World.”

Oddly enough, this same region hosts rare forms of plants related to the pineapple that have resorted to the same strategy for survival.  Two forms of bromeliads, a large and colorful family of tropical plants, many of whom reside as epiphytes high in the rain forest canopy, turn to carnivory atop the tepuis.  Most bromeliads could have resorted to this mechanism but have instead taken a simpler route of using the container formed by their leaf rosette to function as a water storage and a collector of organic detritus that rains from the canopy (in essence, an inverted root system).  On the tepuis, these pitcher-plant mimics have taken the next step: capturing and extracting nutrients from insects.  The rosette of leaves forms a very effective pitcher, complete with steep slippery sloping leaves and an ample water supply for drowning and holding insects.  Aided by bacteria, they extract nutrients from the decaying bodies of prey as they are broken down by their microscopic companions.  But evolutionary speaking, this was a dead end for bromeliads.  No other bromeliads discovered so far have developed this ability.   While the shape of the plant is interesting, overall the carnivorous bromeliads of the tepuis are perhaps the dullest looking members of the entire bromeliad family.  For those who would want to grow them, ideal growing conditions would be identical to those required by the sun pitchers, with whom they often grow.  It seems that this region of the world combines a number of unique climate and soil features that leave plants with little alternative but to resort to predatory practices in order to compete and survive. 

 

North America’s Sun Pitcher Descendants

 

Thousands of miles to the north, in a sandy coastal swamp not too far from the Atlantic Ocean, tall grasses sway in the warm breeze.  Long needled pines form a crescent like a green amphitheatre, facing a lonely two-lane highway.  Streams meander and disperse so that in places they fan out saturating the ground.  Broken blackened tree stumps and branches lay scattered about.  Everything is still slightly damp from the morning dew, but the May sun is already warming the air causing the leaves to give off faint wisps of evaporating moisture.  Bees weave between flower stalks performing their annual pollination rounds unaware of the quiet dangers that lurk almost camouflaged in the grass.  Inflated tubes of varying shapes and sizes stretch gracefully out of the sand, some with gaping lidded maws lined with red veins, luring insects, friend and foe, to an unseen death. 

 

North of the equator reside two other groups of pitcher plants related to the Heliamphora.  Genus Sarracenia contains 9 species, most of which are native to the southeastern United States.  The Sarracenia species assume one of four basic forms: tall trumpet-shaped pitchers with large lids (S. flava, S. leucophylla), narrow tube shaped pitchers with smaller hooded or hood-like lids (S. rubra, S. minor), low-rosettes of fat lid-less vase-shaped pitchers (S. purpurea), and prostate rosettes of parrot-shaped traps that function as both pitchers and underwater traps (S. psittacina).  Most are large hardy plants found in lowland swamps.  Sarracenia purpurea has the largest range, which extends from the Midwest to the East Coast and across much of southern Canada.  Like the Heliamphora, the purple pitcher plant has a very simple trapping mechanism, but nonetheless successful, if its abundance is any indication.

The evidence suggests that the northern cousins evolved from and are arguably more advanced than the sun pitchers.  Aesthetically, they differ in that it is generally not immediately apparent that the tube was ever a leaf.  The coloration of the traps is also more intricate – in some there are prominently colored veins, or distinctively hued hoods, and it is often easy to mistake a North American pitcher plant trap for a flower.  Other aspects of the trapping mechanism are also more sophisticated.  For example, several species use a combination of a hooded pitcher and a series of semi-transparent “windows” that line the back of the pitcher to confuse insects so that they are unable to find the real entrance to the pitcher.  The prey tire themselves out attempting to exit through the false windows and then fall into the trap.  Trap structure and internal surfaces are also better designed for trapping and retaining prey.  The pitchers tend to be more uniformly tube-shaped, and use waxy surfaces and large downward pointing hairs to ensnare and retain prey.  The lids tend to be much better developed in most of the northern species as well, serving as miniature umbrellas to shield the pitcher from rain.

Sarracenia readily hybridize with one another, which suggests that most of the species emerged relatively recently.  Many natural hybrids occur when two species habitats overlap, and these hybrids are often fertile, meaning that they can successfully set seed when pollinated.  Hybrids tend to be more vigorous in many cases as well.  Both the coloration and the trap size and shape tend to combine traits from both parents.  Some  nurseries and hobbyists that specialize in growing Sarracenia species have develop their own hybrids, sometimes crossing one hybrid with another species or hybrid to achieve a particular shape or coloration, just as orchid growers do.  Sarracenia pitchers are sometimes even used in flower arrangements.  Sarracenia flowers are uniquely shaped, and it is a matter of taste whether one considers them attractive.  They range from green to yellow to red and purple.  The reproductive portion of the flower is covered by a structure that resembles an upside-down umbrella.  It tends to be the less colorful portion of the flower, and hangs downward.  Four petals extend outward from the bobbing inverted flower head.  Each flower is borne on its own stem, unlike Heliamphora flower spikes, which usually have multiple flowers.  Sarracenia can be tricky to grow because most experience seasonal variations in nature.  In some areas, the plants experience several months of hot dry weather during the summer, and in others, they endure long cold winters.  Species that live in the middle latitudes of the Sarracenia range have adapted to both extremes, and those tend to be the trickiest to grow.

Across the continent in the cool and rainy Pacific Northwest region grows the third group of plants related to the Heliamphora, represented by a single species in its own separate genus – Darlingtonia californica.  This plant is commonly referred to as the cobra plant.  Several features have lead to this name, including a twisting upright stance, numerous transluscent windows in the downturned head which resemble scales, and most striking of all, a forked appendage that extends out from below the pitcher entrance looking for the world like an oversized snake’s flicking tongue.  The plant only vaguely resembles the sun pitchers, but shares a similar growth pattern with many of its southern cousins in that it forms vast clumps wherever growing conditions suit it, as its underground stems spread.  The flowers of the cobra plant also bear a closer resemblance to Heliamphora than to Sarracenia.  The green or deep red blossoms occur singly and look like small bells.   In some ways, the flowers appear to be an intermediate form between Heliamphora and Sarracenia, for while retaining a delicate appearance like the sun pitchers, they are surrounded by dangling petals like those found in their eastern cousins. 

Darlingtonia employs some of the same trapping features that some types of Sarracenia have.  S. minor has numerous small translucent windows that dot the back of the hood opposite the entrance.  Both it and the cobra plant both depend on this feature to confuse prey and cause them to tire and fall and drown in the liquid their traps contain.  Like the trumpet shaped species of Sarracenia, the Darlingtonia pitcher is tall and gradually narrows.  Like the parrot pitcher plant (S. psittacina), the cobra plant’s hood extends and encompasses the entrance, so that it is a small hole rather than a gaping vase rim.  Also like some Sarracenia, juvenile Darlingtonia traps often lay down towards the ground, where they can capture crawling insects. But the adult leaves of cobra plants assume an upright form.  They twist outward from their underground growth tip up to 180 degrees and can grow as tall as four feet, making them the longest individual traps borne by any carnivorous plant in the world.

Cobra plants prefer consistently cool locations, with morning fog, frequent rains, and some sun.  The plants tend to cluster alongside mountain streams in western Oregon and northern California, often clinging to the hillsides in locations one would normally consider unlikely for a large carnivorous plant.  They are often found with butterworts and sundews that live in the same region.  When they occur at lower altitudes, it is often at points where small mountain streams or springs flow and spread out to form small swamps open to the sky.  Because of this fondness for mild temperatures and cool fresh flowing water, they can be challenging to grow.  They are rather compatible with Heliamphora species, but are stunted and eventually die in conditions that ideally suit Sarracenia.  Nonetheless, their unique form has made them among the most well-known and widely available carnivorous plants other than the famous flytraps. 

 

The Nepenthes of Tropical Asia, Australia and Africa

 

Half way around the globe, on the slopes of a massive tropical mountain, tantalizing glimpses suggest that there’s something unusual trailing through the tropical shrubs.  A clearing offers a better view of a broad leafed scrambling vine accompanies by ovoid white tubs that seem to dangle in mid-air.  Every bush in site seems to bear some of these urns that give them the appearance of being in full bloom, albeit with peculiarly shaped “blossoms.”  Closer inspection reveals that the blossoms are pitchers attached by a thin, sometimes curled or looped stem that attaches to the broad leathery strap shaped leaves at their tip.  Encircling the entrance to these traps are broad candy-striped rims, each with a slightly varying pattern of light and dark shades of maroon and purple.  Ants occasionally scurry across a pitcher or the overhanging lids that seem large enough to prevent rainwater from filling and overflowing them.  The water inside appears clear, but just visible is a tangle of insect and arthropod limbs jutting from a murky sludge that lines the bottom of each pitcher.

 

Even more widespread and diverse than the pitcher plants of the Americas are the tropical pitcher plants that grow from Madagascar and Australia to Malaysia and into China.  Some seventy known species fill niches that include rocky sea cliffs, lowland swamps, cool highland forests, and even roadside ditches where development encroaches upon their territory.  Most take the form of climbing or scrambling vines.  Unlike other pitcher plant species where the entire leaf forms various components of the trapping mechanism, Nepenthes retain a fully functional oval to strap-shaped leaf, from which emerges a tendril which is often used for climbing, and it is the tip of this tendril that develops into a trap.  It is one of the most complex leaf forms in the plant kingdom. 

Nepenthes populations dot three continents and numerous islands, small and large, but there are clusters of species in three locations.  Borneo is home to the largest number of species (more than 30), followed closely by Sumatra (number in the 20s), while other regions including the Malaysian peninsula, New Guinea and the Philippines each host more than ten distinct species.  Despite these modern day strongholds clustered around the equator, some believe that the species originated on the Indian subcontinent over 80 million years ago.  In northern India, in the state of Assam, lives a highland species called Nepenthes khasiana.  It has long pale green leaves and long, but otherwise unspectacular pink or red-tinged pitchers the entrance to which is encircled by a simple round reddish rim or lip (called a peristome) lined with minute corrugated ridges.  It has all the basic features of a pitcher plant, but little of the flair found in other species.  Madagascar hosts two primitive scrambling shrub species (N. madagascariensis, N. masoalensis) that prefer lowland swamps, smaller in form but similarly simple in design, with medium sized trumpet shaped pitchers. Scientists believe that one of these plants is closely related to the ancestral form that gave rise to all Nepenthes living today.  Was the first Nepenthes a swamp scrambler from off the coast of Africa? Or was it a plant similar to the robust high climbing Indian pitcher plant that paved the way for the myriad of often spectacular pitcher plants that have become so successful thanks in part to their carnivorous nature?  The question may never be answered with complete certainty, but the fact that a significant majority of the Nepenthes species are highland would tend to lend some support to N. khasiana as a leading candidate for one of the closest living relatives to the ancestor of all modern Nepenthes species.

Below 1000 meters in altitude, Nepenthes that occur in tropical regions are used to warm days and nights, and lots of moisture and high humidity.  They occur in swamps, alongside streams and roads, and some even in the forest itself.  Like N. khasiana, there are many varieties of Asian pitcher plants that are variations on the strap leaf/tubular pitcher form, with modest adjustments in shape, and significant color variations.  Highland species have a slight edge in terms of spectacular forms, but the lowland species hold their own with such amazing species as Nepenthes ampullaria, bicalcarata, rafflesiana, and veitchii. 

The large leafed, diminutive pitchered N. ampullaria is something of a mystery among Nepenthes species in that it seems to rarely produce upper pitchers.  Most Nepenthes produce at least two distinct forms of pitchers during their lifecycle.  Lower pitchers are generally more oval or tub-shaped, and often larger, because at this stage the plant is still growing close to the ground.  Some plants spend years growing as a flat rosette with no discernable stem, or scrambling along the ground, where these sorts of traps are effective at capturing scores of beetles and ants and other ground-dwelling insects.  Upper pitchers are often trumpet or goblet-shaped, so they contain less water and are therefore easier for the climbing plant or nearby shrubbery to support.  N. ampullaria produces clusters of peculiar tub-shaped pitchers with a small ineffective lid.  Sometimes the pitchers appear to emerge directly from the soil, because the leaf and tendril are significantly reduced.  Once the plant starts to climb, pitchers occasionally appear in clusters along the stem, but tend not to form at the ends of its long fuzzy leaves as it reaches for the canopy.  Some suggest that perhaps this pitcher plant is abandoning carnivory – but only time will tell for sure. 

Nepenthes rafflesiana is the archetypal large swamp dwelling Nepenthes.  Tolerant of heat and moisture, its long leathery leaves bear lower and upper pitchers that differ dramatically.  The lower pitchers are fat cups mottled purple or red on a cream-colored background.  Another characteristic is a pair of frilled wings that cling to the front of the pitcher and lead to the prominent candy striped rim.  The rim is shaded by lid about the size of the mouth and is held high atop a vertical extension of the rim trimmed with parallel rows of short spines.  The upper pitchers are long, trumpet-shaped, green, with two prominent ribs replacing the wings, and a more subdued and the rim is almost pouting in appearance. 

Nepenthes bicalcarata is of similar form to N. rafflesiana, but less colorful.  An orange or rust color replaces the mottled pattern, smaller wings and a simpler rim replace the candy striped pitcher entrance, but under the lid occurs a most peculiar structure, to which a few fantastic purposes have been ascribed.  Two sharp, well-developed thorns emerge from under the lid, and overhang the pitcher itself, giving the pitchers a particularly vicious predatory appearance.  Some have suggested that the “fangs” are used to ensnare small mammals that sometimes drink from or rob pitchers.  But the plant has relatively small pitchers and no evidence has been presented to support this fantastic theory.  The plants do seem to have a complex relationship with ants, even providing living quarters for the insects in the enlarged tendril that attaches the pitcher to the leaf, so some speculate that the “fangs” play some role in that relationship, though probably not a beneficial one for the ants. 

Nepenthes veitchii is one of the more spectacular lowland Asian pitcher plants, and is often used in the development of hybrids because of its unique traits.  The plant itself is distinctive in that it tends to be covered with dense reddish or gold hairs, and prefers to clasp itself tightly to the trunks of trees rather than the more typical haphazard approach of clinging to neighboring branches via tendrils.  Short oval leathery leaves appear in alternating fashion and cling tightly to the host tree as the vine climbs upwards.  These leaves produce short tendrils with flamboyant pitchers as large as the leaves themselves.  The pitchers are usually yellow-green, with a pair of frills running up the front to an extremely well-developed rim.  The broad corrugated rim expands around the entrance and up to the lid where it forms a showy flower-like collar, green with randomly alternating bands of narrow and wide red stripes.  The lid is held up and outward and while narrow, still serves as an effective umbrella during downpours.  While other Nepenthes share some of the showy characteristics of this plant, it is unique in its tree-hugging growth habit. 

Lowland Nepenthes as a group tend to be easier to grow than their highland cousins, because their growing requirements remain constant, just as the tropical environment to which they have adapted. High humidity, indirect light, and consistent warm temperatures produce rapid growth among most species.  They have very low tolerance for cool temperatures, and many will suffer damage if the temperature drops below 50 degrees Fahrenheit. 

Highland Nepenthes species tend to occur on tropical mountains above 1000 meters. At these altitudes the days are still warm and sometimes sunny, but the mountains tend to be shrouded in fog daily, and the nights are cool especially at increased elevations.    Some of the largest pitchers, including one capable of trapping small mammals, are found on plants growing in high tropical mountains in Borneo and the Philippines.  N. rajah from the Malaysian state of Sabah, and N. merrilliana from the Philippines have the largest pitchers in terms of volume and overall dimensions.  Both bear bulbous, cylindrical pitchers with wide peristomes and large overhanging lids as they scramble amongst the stunted high mountain vegetation.  Both have ample capacity to capture and digest small rodents, and N. rajah has been confirmed to do so, although the rats that fell victim to the traps were probably seeking water rather than lured by the trap’s coloration or promise of nectar.  Several highland species have very coarsely ribbed peristomes.  These species, which include N. edwardsiana, N. villosa, and N. macrophylla assume an almost industrial-mechanical appearance due to the widely spaced ribs that line the rim of the pitcher.  Since the wide spacing of the ribs affects the ability of the rim prevent small prey from escaping the pitcher, it is possible that this form is better adapted to retaining larger insects such as large beetles.  Other highland species of note are N. burbidgea, which has large beautiful white pitchers splotched with red, and the highly variable N. maxima with its heavily speckled red pitchers and numerous forms ranging from simple cylinders to complex French horn-like shapes. 

A few highland species appear to be evolving the ability to capture something other than insects.  Nepenthes lowii, N. ephippiata, and N. inermis have developed a different shape that seems ill-suited to insect capture.  The peristome in the upper pitchers of these species has shrunken to the point where it can no longer serve as an egress deterrent for prey.  The mouth of the pitcher has greatly expanded so that it is typically wider than the pitcher itself, and the lid has either shrunk or been moved so that it no longer covers the mouth of the pitcher.  In fact, pitcher shape in these species is quite similar to that of the modern flush toilet!  Field observations seem to suggest that the plant may depend on collecting bird droppings.  N. lowii in particular seems to have developed an attractant in its lid that entices birds to the pitchers.  If this is true, then these plants are technically no longer carnivorous, but are still unique.

Like the North American pitcher plants, Nepenthes hybridize readily, and natural hybrids are often found in nature where two species overlap.  Indeed, during the Victorian era after the advent of the Wardian cabinet (a stylized glass terrarium that resembles a miniature conservatory), Nepenthes hybrids were quite popular in Britain, and many were developed prior to and later lost during World War II. Many Nepenthes hybrids exhibit exceptional vigor in cultivation, and sometimes they exceed the size and growth rate of either parent.  Given the volatile nature of their environment where frequent storms or monsoonal rains pair up with other forces of nature including landslides and volcanism to frequently reshape the landscape, the tropical pitcher plant’s ability to hybridize and rapidly try out new forms has surely contributed to its success.

 

The Diminutive Australian Pitcher Plant: Convergent Evolution?

Lady slipper orchids often form a moccasin-like pouch as part of their flower structure, and at least one carnivorous pitcher plant utilizes virtually the same slipper-shaped form to capture insects.  In a small corner of Western Australia, nature used a completely different mechanism to construct the familiar pitcher trap, yet arrived at a remarkably similar form.  In the winter the small bog plant called Cephalotus follicularis consists of clusters of inconspicuous oval shaped dark green leaves, but it also manages to produce intricate pitchers that rival the most elaborate Nepenthes pitchers when weather conditions are favorable for insects.  Cephalotus ignored the pitcher formation model perfected by the Nepenthes, so its pitchers are not formed from a curled funnel, but rather a folded leaf (tip to stem).  The small green moccasins face outward from the cluster of trapping and non-trapping leaves, awaiting prey.  The only clue that demonstrates that this pitcher forms differently than those of other pitcher trap plants is the stem that emerges from the upper back part of the pitcher, not far below where the lid is attached to the plant. No other pitcher plant in the world grows this way and Cephalotus has convergent evolution to thank for its uniqueness.

Australia is a land rich with examples of convergent evolution.  Among its marsupial population, there are or have recently been animals that occupy predator and grazer niches filled by placental mammals on other continents.  Amazingly enough, the marsupial equivalents often bear a strong resemblance to their placental equivalents.  For example, kangaroos, while having obvious differences from whitetail deer, still bear a strong resemblance to them, particularly in terms of mobility and structure of the head and ears.  The more-or-less extinct (depending on the reliability of reported sightings and science’s impending attempts to clone and revive it) Tasmanian tiger is strikingly canine-like.  The Australian pitcher plant is no less amazing.  It took a radically different path but ended up with a remarkably similar and equally sophisticated solution to similar environmental demands as experienced by pitcher plants around the globe.

Cephalotus pitchers tend to be 6-10 centimeters in length, with three hairy ribs down the front (compared to two in Nepenthes), a large corrugated lid that protects the mouth of the pitcher from rain, and a coarsely ribbed peristome that encourages entry but prevents escape with downward pointing teeth, which strongly resembles Nepenthes villosa, N. hamata, and related plants. Large flower spikes containing a number of small white star-shaped flowers grow up to 2 feet above the pitchers, presumably to avoid the plant inadvertently capturing pollinators. 

As with North American pitcher plants, because it evolved in a region with fairly well-defined seasonal variations, it can be difficult to grow and maintain.  Like Darlingtonia, it is fond of locations near flowing water.  In cultivation, Cephalotus can be difficult to coax into producing pitchers.  But it is well worth a try given that they rival Nepenthes in their complexity and elegance of design. 

 

Conclusion

Three times, nature built pitcher plants.  On at least three separate occasions, nature saw fit to convert the humble leaf into a well-disguised trapping and digestive mechanism that enabled some lucky plants to colonize and flourish in conditions that few other plants found suitable.  Some traps are simple, converted broad leaves that folded lengthwise, perhaps initially collecting litter from other plants and trees.  But they were always trying new mechanisms from their inventory of forms by using instructions in their DNA that had served them so well in their efforts to lure pollinators, until they found a suitable form to attract, capture and digest prey.  Like the flowers they mimic, they combine colors and shapes and even on occasion scents that both people and insects find attractive.  And for millions of years, insects have paid for that infatuation with their lives.  Nature marches onward even today as pitcher plants, some already used to environmental change, cling to roadsides and explore new food sources. 

As with many plants and animals in the world today, most are under pressure or endangered, both from habitat destruction and over-collecting by hobbyists.  But thanks to the efforts begun in the early nineties to clone and mass produce these rare plants from tissue culture, many species are likely to be preserved from extinction despite pressures on their natural habitat.  Perhaps they will survive long enough under our care that man will halt and reverse some of the damage, and then be returned to stealthily hunt again in the lands that gave birth to them.