Lemna perpusilla
Content
Description
Small floating aquatic.
Ovary with 1 orthotropous ovulum, style sub-apical, persistent.
Fruit asymmetric, ellipsoid, laterally slightly compressed.
Seed with 12-18 distinct longitudinal ribs, laterally slightly compressed.
Distribution
Ambon present, Aru Is present, Asia-Tropical: Borneo (Sabah present); Malaya (Peninsular Malaysia present); Maluku (Maluku present); Philippines (Philippines present); Sumatera (Sumatera present), Enggano present, Flores Sea present, Hawaian Is present, Kangean Is present, Lesser Sunda Is present, Luzon present, Madura present, Maikoor present, Mindanao present, New Caledonia present, Pacific: Fiji (Fiji present); Samoa (Samoa present); Tonga (Tonga present), Pacific Islands present, Tanah Djampea present, Timor present, W.-E. Java present, W.-E. New Guinea present, Worldwide in the tropics and sub-tropics present
Worldwide in the tropics and sub-tropics. In the Pacific islands in several Hawaian Is. (first 1895), Samoa (1893), Tonga (1926), Fiji (1842), New Caledonia; common in Malesia: Sumatra (also Enggano), Malay Peninsula, W.-E. Java (also Madura&Kangean Is.), Lesser Sunda Is. (Timor), Flores Sea (Tanah Djampea), North Borneo, Philippines (Luzon to Mindanao), Moluccas (Ambon; Aru Is.: Maikoor), and W.-E. New Guinea.
Notes
BACKER (1924) was the first to point out that L. minor does not occur in Malesia; he referred this material to L. paucicostata.
L. perpusilla is an extremely variable species. HEGELMAIER (1868) distinguished in his monograph 3 species, viz L. perpusilla (seed with 30-60 ribs, restricted to the eastern part of the U.S.A.), L. paucicostata (seed with 12-20 ribs, occurring in the tropics of the Old and the New Worlds; also in the S. and SE. parts of the U.S.A.) and L. angolensis (seed with 12-15 ribs, and moreover a conspicuous apical papilla on the frond, restricted to tropical Africa). L. angolensis, already earlier described a.sL.aequinoctialis byWELWiTSCH, is with respect to the seed character within the range of variation of L. paucicostata. The development of the apical papilla on the frond is subject to so much variation, even within one sample, that it is not useful as a specific character. THOMPSON () who investigated L. perpusilla and L. paucicostata in the U.S.A. found the number of ribs on the seeds of these species so variable that he could not distinguish the species with certainty, and for that reason he regarded them as forms of one species.
Some flat, membranous forms with a distinct venation, but otherwise not different from L. perpusilla, have been distinguished as L. perpusilla var. trinervis, L. paucicostata var. mem-branacea or as L. trinervis. They have been recorded from America and India. In my opinion they represent only forms of L. perpusilla, induced by poor environmental circumstances. MCCLURE & ALSTON (), however, found L. trinervis to be quite distinct from L. perpusilla with respect to the flavonoid chemistry. Therefore, membranous forms require re-investigation.
The fronds from New Guinea are often twice as long as wide, in contrast to those from the rest of Malesia.
MERRILL () referred L. gibba (non L.) BLANCO to L. paucicostata (= L. perpusilla). As BLANCO recorded the occurrence of 2 roots, his plants must have belonged to Spirodela punctata. MERRILL'S representative specimen Sp. Bl. 131 belongs to L. perpusilla.
L. perpusilla is an extremely variable species. HEGELMAIER (1868) distinguished in his monograph 3 species, viz L. perpusilla (seed with 30-60 ribs, restricted to the eastern part of the U.S.A.), L. paucicostata (seed with 12-20 ribs, occurring in the tropics of the Old and the New Worlds; also in the S. and SE. parts of the U.S.A.) and L. angolensis (seed with 12-15 ribs, and moreover a conspicuous apical papilla on the frond, restricted to tropical Africa). L. angolensis, already earlier described a.sL.aequinoctialis byWELWiTSCH, is with respect to the seed character within the range of variation of L. paucicostata. The development of the apical papilla on the frond is subject to so much variation, even within one sample, that it is not useful as a specific character. THOMPSON () who investigated L. perpusilla and L. paucicostata in the U.S.A. found the number of ribs on the seeds of these species so variable that he could not distinguish the species with certainty, and for that reason he regarded them as forms of one species.
Some flat, membranous forms with a distinct venation, but otherwise not different from L. perpusilla, have been distinguished as L. perpusilla var. trinervis, L. paucicostata var. mem-branacea or as L. trinervis. They have been recorded from America and India. In my opinion they represent only forms of L. perpusilla, induced by poor environmental circumstances. MCCLURE & ALSTON (), however, found L. trinervis to be quite distinct from L. perpusilla with respect to the flavonoid chemistry. Therefore, membranous forms require re-investigation.
The fronds from New Guinea are often twice as long as wide, in contrast to those from the rest of Malesia.
MERRILL () referred L. gibba (non L.) BLANCO to L. paucicostata (= L. perpusilla). As BLANCO recorded the occurrence of 2 roots, his plants must have belonged to Spirodela punctata. MERRILL'S representative specimen Sp. Bl. 131 belongs to L. perpusilla.
Citation
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