Is that right, or left?
The Right-Hander, Dextropinnum herbaceum, can be seen behind a young Pinnatidendron in the picture at right. All the leaves on this plant are pinnate, but the pinnae are on the right side of the rachis only. The position of the pinnae is seen by looking at the upper surface of a leaf in front of you, with the petiole oriented vertically. All the pinnae are then seen to be present on the right side of the leaf.
This plant grows from a rhizome that creeps horizontally along the surface of the ground, with leaves held such that the pinnae face forward. Each leaf is accompanied by a relatively inconspicuous axillary inflorescence.
The genus Dextropinnum was named before a thorough exploration of Aroidia was completed. Later investigations revealed that when these plants grow at the equator, the pinnae develop in a spiral pattern around the rachis. Those growing in the southern hemisphere have pinnae oriented on the left side of the rachis! Intermediate forms with semi-spiraling pinnae have been observed just to the north and south of the equatorial zone.
At left is a young specimen of Dextropinnum herbaceum, showing the overall habit. Note the creeping rhizome detail and the very narrow axillary inflorescences.
This genus has genetic affinities to Pinnatidendron, but grows nowhere near as large as that plant.
Blooming with forked tongue
Cryptospadia herpeto-lingua, the Snake Tongue plant, is our next specimen. This beauty has heavy, stiff leaves and most unusual axillary inflorescences. Cryptospadia spathes are split like a snake's tongue and the two splits wrap lightly around the petiole of the host leaf. The spadix starts out as a very short thin structure held very close to the spathe. It is set so low in the spathe that it cannot be seen, hence the name, Cryptospadia, or "hidden spadix" (picture at right). Once the pollenoids have done their thing, however, this hidden spadix enlarges dramatically to emerge into full view as a thick, erect, sausage-like cluster of berries (picture at left).
Cryptospadia plants grow 4 feet tall, in full sun, generally preferring sites within 5 to 10 feet of the waterline. A typical specimen will have no more than four leaves and a single inflorescence present at one time.
That "palm" is an Aglaonema?
On Earth a well-known aroid genus is Aglaonema. These are relatively small sized plants that are suitable for use as indoor or house plants. On Aroidia, however, is found the species Dendroaglaonema undulata, a massive treelike aroid with a trunk that resembles those of some palms on Earth. Another species, Dendroaglaonema alta, has a very tall, thin trunk with clusters of inflorescences hanging below the crown of leaves. Dendroaglaonema undulata grows a thick trunk, wavy lanceolate leaves, very large showy inflorescences and berries about the size of a coconut.
At left is an example of Dendroaglaonema undulata, with one stalk having matured enough for blooming. Note the inflorescence, infructescence, new shoots and remains of old trunks. The stumps are what the annual storm season left behind. These plants grow exceptionally fast, ascending to 20 feet in height within just one season. Specimens growing in more protected latitudes will retain the larger stalks and grow up to 50 feet tall. Dendroaglaonema alta grows even taller, reaching close to 80 feet with its relatively slender trunk and durable cordate leaves.
More to come
I've visualized many other species and genera on Aroidia. A few among them are Principearum, the Palm Arum, Calliopsis, Laterophyllum, Pseudo-sauromatum, Rhizophyllum, the Upside-Down Arum and Pseudoanthurium. These plants, plus many more species in genera already described, are examples of diversity still to be manifested in plants of a family we all know and love, the Aroid family!
Sharing my imaginative journey with you has been a joy for me and I hope you, too, have enjoyed the adventure. Now that I look at today's date, I see that Spring is practically upon us. That means it is time for me to get back to developing new aroids here on Earth. However, I do plan to visit Aroidia again next winter, and hope you all will join me then for more exciting discoveries and education.
Picture credits: LariAnn Garner, Aroidia Research