arum lily

Arum family Fossil range: 70–0 Ma PreЄ Є O S D C P T J K Pg N Late Cretaceous[1] - Recent
Flower of Xanthosoma roseum
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Alismatales
Family:	Araceae Juss.
Genera
See text.

Peace Lily (Spathiphyllum cochlearispathum) clearly showing the characteristic spadix and spathe.

Araceae is a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like hood. The group also goes by the name of Arum family and species in this family are often colloquially known as aroid. This family of 107 genera and over 3700 species is most diverse in the New World tropics, although also distributed in the Old World tropics and north temperate regions. Recent genetic research by the Angiosperm Phylogeny Group has shown that the duckweeds, previously treated in a separate family Lemnaceae, also belong in the Araceae family.

Anthurium and Zantedeschia are two well-known members of this family, as are Colocasia esculenta (taro) and Xanthosoma roseum (Elephant ear or ‘ape). Among the largest inflorescence in the world is that of the arum, Amorphophallus titanum (Titan arum). This family includes a great many ornamental plants: Dieffenbachia, Aglaonema, Caladium, Nephthytis, and Epipremnum, to name a few. In the genus Cryptocoryne are many popular aquarium plants. Both Taro and Monstera deliciosa provide food value (the fruit of Monstera deliciosa called "Mexican breadfruit"). Philodendron is an important plant in the ecosystems of the rainforests and is often used in home and interior decorating. Symplocarpus foetidus (skunk cabbage) is a common North American species. An interesting peculiarity is that this family includes the largest unbranched inflorescence, that of the titan arum, often called the largest flower in the world.

The Cuckoo-pint or Lords and Ladies (Arum maculatum) is a common arum in British woodlands

Description

Species in Araceae are often rhizomatous or tuberous and are often found to contain calcium oxalate crystals or raphides. The leaves can vary considerably from species to species. The inflorescence is composed of a spadix, which is almost always surrounded by a modified leaf called a spathe.In monoecious aroids (possessing separate male and female flowers, but with both flowers present on one plant), the spadix is usually organized with female flowers towards the bottom and male flowers towards the top. In aroids with perfect flowers the stigma is no longer receptive when the pollen is released, thus preventing self-fertilization. There are also some dioecious species.

Many plants in this family are thermogenic (heat-producing). Their flowers can reach up to 45 degrees Celsius even when the surrounding air temperature is much lower. One reason for this unusually high temperature is to attract insects (usually beetles) to pollinate the plant, rewarding the beetles with heat energy. Another reason is to prevent tissue damage in cold regions. Some examples of thermogenic Araceae are: Symplocarpus foetidus (eastern skunk cabbage), Amorphophallus titanum (Titan Arum), Amorphophallus paeoniifolius (elephant foot yam), Helicodiceros muscivorus (dead horse arum lily) and Sauromatum venosum (voodoo lily). Species such as Titan Arum and the dead horse arum give off a very pungent smell, often resembling a rotten animal. This is to attract flies to pollinate the plant. The heat produced by the plant helps to convey the scent further.

History

One of the earliest observations of species in Araceae was conducted by Theophrastus in his work Enquiry into Plants. It wasn't until the 16th century that Araceae was recognized as a distinct group of plants. In 1789 Antoine Laurent de Jussieu classified all climbing aroids as Pothos and all terrestrial aroids as either Arum or Dracontium in his book Families des Plantes. It wasn't until Heinrich Wilhelm Schott published Genera Aroidearum in 1858 and Prodromus Systematis Aroidearum in 1860 that major classification progress was made in the family. At the time of writing these books Schott was only aware of approximately 900 species that he subsequently classified into 12 tribes. These 12 tribes grew to become the primary framework from which all subsequent classification was based.

The largest collection of living Araceae is maintained at Missouri Botanical Gardens.^[2] Another large collection of living Araceae can be found at Munich Botanical Garden, thanks to the efforts of the researcher and aroid authority Josef Bogner.

Toxicity

Some or all genera in the the Araceae Family contain calcium oxalate crystals whose effects can cause anything from minor skin irritations to total vision loss and—if enough is consumed—death. Genera such as Alocasia, Arisaema, Caladium, Colocasia, Dieffenbachia, Philodendron.

Genera

Subfamily Aroideae

Subfamily Calloideae

• Calla L.

Subfamily Gymnostachydoideae

• Gymnostachys R. Br.

Subfamily Lasioideae

• Anaphyllopsis A. Hay
• Anaphyllum Schott
• Cyrtosperma Griff.
• Dracontioides Engl.
• Dracontium L.
• Lasia Lour.
• Lasimorpha Schott
• Podolasia N. E. Br.
• Pycnospatha Thorel ex Gagnep.
• Urospatha Schott

Subfamily Lemnaoideae

• Landoltia
• Lemna
• Spirodela
• Wolffia
• Wolffiella

Subfamily Monsteroideae

• Alloschemone Schott
• Amydrium Schott
• Anadendrum Schott
• Epipremnum Schott
• Heteropsis Kunth
• Holochlamys Engl.
• Monstera Adans.
• Rhaphidophora Hassk.
• Rhodospatha Poepp.
• Scindapsus Schott
• Spathiphyllum Schott
• Stenospermation Schott

Subfamily Orontioideae

• Lysichiton Schott
• Orontium L.
• Symplocarpus Salisb. ex W. P. C.
  Barton, nom. cons.

Subfamily Pothoideae

• Anthurium Schott
• Pedicellarum M. Hotta
• Pothoidium Schott
• Pothos L.

Subfamily Zamioculcadoideae

• Gonatopus Hook. f. ex Engl.
• Zamioculcas Schott

Notes

References

• Bown, Deni (2000). Aroids: Plants of the Arum Family [ILLUSTRATED]. Timber Press. ISBN 0881924857
• Croat, Thomas B (1998). "History and Current Status of Systematic Research with Araceae". Aroideana 21.  on line
• Grayum, Michael H (1990). "Evolution and Phylogeny of the Araceae". Annals of the Missouri Botanical Garden 77 (4). 
• Keating R C (2004). "Vegetative anatomical data and its relationship to a revised classification of the genera of Araceae". Annals of the Missouri Botanical Garden 91 (3): 485–494. 

External links

• CATE-Araceae (and Network Araceae)
• An interactive key to the genera of Araceae

Wikimedia Commons has media related to: Araceae