Hygrophila

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Hygrophila

Hygrophila polysperma in an aquarium

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Lamiales
Family:	Acanthaceae
Genus:	Hygrophila Lindl.

Selected species

Hygrophila, commonly known as the temple plants or hygros, is a genus of flowering plants in the family Acanthaceae. There are about 125 species, of which about 40 are aquatic. The genus has a pan-tropical distribution, with some members entering sub-tropical areas. It is one of only two genera in its family that contains aquatic plants, the other being Justicia. The genus is treated inside the tribe Hygrophileae, which is noted as being in need of revision at the genus level, meaning the current taxonomic boundaries of Hygrophila are likely to change in the future.^[1]

1 Description
2 Ecology and uses
3 References
4 External links

[edit] Description

The leaves are either homomorphic (i.e. all having one form) or heteromorphic (i.e. different leaves having different forms). When they are homomorphic, they are always simple and entire. When heteromorphic, the basal or submerged leaves are pinnately divided with either filiform (i.e. feather-like) or linear segments that can be either simple or forked, while the cauline leaves (i.e. those on the stem) or emergent leaves are entire.^[1]

The flowers have petals ranging from white to purple in colour, having either 5 equal lobes or 2 lips. When an upper lip is present, it is erect and concave with either 2 lobes or 2 teeth, while the lower lip has 3 lobes. 4 stamens are present with 2 sometimes being staminodal (i.e. non pollen producing). They are not exerted and are fused to the petal tube above the middle. The individual filaments are united into pairs by a membrane at their bases, while the anthers have 2 locules. The anther sacs have no spurs or tails and are at the same level and parallel. A nectariferous disc is present but inconspicuous. Pollen grains are 3- or rarely 4-colporate, meaning the apperatures are composed of both a colpus and a porus. Each flower produces 6 to many seeds.^[1]

[edit] Ecology and uses

A number of species are cultivated for the aquarium trade, including H. difformis (water wisteria) and Hygrophila polysperma (Indian swampweed). Many members of the genus are troublesome weeds in irrigation and drainage ditches as well as ricefields. Several have become established outside of their native ranges, largely due to the aquarium trade, such as H. polysperma in the southern United States. ^[1]