Diversity: Perennial herbs,
often terrestrial or climbing via adventitious roots, rarely floating aquatic
(Pistia). Many taxa have extended their tropical range
into termperate offices and homes as foliage ornamentals (Philodendron,
Dieffenbachia, Monstera) and Colocasia
esculenta is an important food plant of the tropics (taro, poi).
The family includes about 110 genera and about 1,800 species.
Distribution: Worldwide
in tropical and subtropical areas with some taxa (less than 10%) extending
into temperate habitats. We have 5 genera and 7 species (3 species of Arisaema)
in Texas.
Floral structure:
Significant features: Variable
vegetatively, although presence of toxic calcium
oxalate crystals (raphides)
is common, and the flowers, highly reduced, are of little value for identification.
The unusual inflorescence provides a strong key character in the
field. Similar to the Asteraceae, small flowers of the Araceae,
either perfect or unisexual, are aggregated on a common receptacle.
This structure, known as a spadix,
is usually elongate with the flowers attached - or embedded - along its
axis. The spadix is usually subtended
by a highly modified bract, knows as the spathe.
This combination - spadix and spathe
- serves as an excellent marker for the family.
Arismaea triphyllum -
'jack in the pulpit'
plant in flower
'jack in the pulpit' (spadix
enclosed by distinctive spathe)
Caladium:
Plant in flower
inflorescence (spadix) with spathe
spadix with spathe removed
Pistia - transition to the
Lemnaceae?
Pistia stratiotes - plants in habitat -
Marco Island, Florida
Pistia stratiotes - plant and inflorescence
(right) - from the University
of Hawaii
