Apium inundatum (L)Reichneb.fil Lesser Marshwort
NOMENCLATURE
Apium: see A. gravolens.
inundatum : submerged, from inundo : flow over.
PREVIOUS NAMES : Helosciadium inundatum (L) Koch.
BOTANICAL DESCRIPTION
TYPE: part/submerged glaborous perennial. Hyd. STEMS: slender, weak, smooth.
HEIGHT: 10-75 cm. UMBELS: compound, leaf opposed with 2(-4)
smooth rays 0.5-1 cm, unequal. Peduncles 1-3.5cm.
LEAVES: lower leaves 2-3 pinnate, segments deeply pinnatifid, lobes filiform. Upper.
pinnate, lancolate to ovate, Segments 0.5-1cm, cuneate, 3 lobes, linear. sessile 5mm long.
BRACTS: bracteoles 3-6, lancolate, obtuse, unequal.
FLOWERS: white. Subsessile styles form a stylopodium. Fl. 6-8.
FRUIT: 2.5-3 mm, elliptic-oblong, laterally compressed, smooth. Commisure narrow.
Mericarps with prominent ridges. Carpophore present. Vittae solitary. Pedicels short.
Styles 1/2 as > as S stylopodium, spreading. Stigma small knob.2n=22.
HABITAT: lakes ponds, ditches.
DISTRIBUTION: native. <500m. Wide but local in Britain.
W. Europe E. to Sicily, S.E. Sweden.
HYBRID: A. x moorei (Syme) Druce : A. inundatum x A. nodiflorum.
Frequent Ire. rare England. leaves simply pinnate, obovate lobes, umbels
with 2-3 rays. Sterile. Sparse flowers.
(Plant B in diagram)
http://www.mpiz-koeln.mpg.de/~stueber/thome/band3/tafel_045_small.jpg