Podostemaceae (redirected from Riverweed family)

Podostemaceae [pə‚däs·tə′mās·ē‚ē]

(botany)

The single family of the order Podostemales.

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Podostemaceae 

a family of dicotyledonous plants including annual or perennial herbs. The plants, which are usually very small, often resemble the thallus of some liverworts, lichens, or algae. The plants grow on rocks, on cliffs, or, less frequently, on tree trunks in fast-flowing water and waterfalls. They often cling to the substratum by means of special hooks called haptera. As a rule, the thallus-like part is of root origin, with secondary shoots usually growing from it exogenously. The alternate leaves are entire or dissected. The tiny, inconspicuous flowers are bisexual; they are solitary or gathered in cymose inflorescences. The fruit is a capsule with very tiny seeds. There are 43 genera, comprising about 200 species.

The plants are widely distributed, mainly in the tropics of America and the tropics and subtropics of Asia and Africa. The members of the family Podostemaceae are an example of the extreme specialization of plants under specific environmental conditions.

REFERENCES

Takhtadzhian, A. L. Sistema i filogeniia tsvetkovykh rastenii. Moscow-Leningrad, 1966.
Engler, A. “Podostemonaceae.” In Die natiirlichen Pflanzenfamilien, 2nd ed., vol. 18a. Edited by A. Engler. Leipzig, 1930.

M. E. KIRPICHNIKOV