482 THE ALISMA FAMILY. [Alisma. 



III. ALISMA. WATER PLANTAIN. 



Aquatic herbs, erect or rarely floating, with radical, long- stalked 

 leaves ; the flowers either in a terminal umbel, with or without whorls 

 of pedicellate flowers below it, or in a panicle with whorled branches 

 each bearing a similar umbel. Perianth of 3 outer, small, herbaceous 

 segments, and 3 much larger inner ones, petal-like, and very delicate. 

 Stamens 6. Carpels numerous, small, and 1-seeded, either arranged in 

 a ring round the axis, or irregularly in a globular head. 



A genus comprising several species, chiefly American, but some of 

 them distributed over nearly the whole world. 



Flowers numerous, in a loose panicle. Carpels forming a ring 



round the axis of the flower 1. A. Flantago. 



Flowers few, in a single umbel. Carpels irregularly arranged 



in a globular head. 

 Stems erect or creeping. Carpels with 4 or 5 prominent 



ribs 2. A. ranunculoidet. 



Stems floating. Carpels with 12 to 15 slender ribs . . . 3. A. natans. 



1. A. Plantago, Linn. (fig. 974). Common W. Rootstock perennial, 

 becoming almost bulbous by the thickened sheathing bases of the leaf- 

 stalks. Leaves radical, varying from ovate to narrow-lanceolate. 

 Flower-stem 1 to 3 feet high, with whorled branches, unequal in length, 

 forming a loose, pyramidal panicle. Flowers rather small, of a pale 

 rose-colour, 'on long whorled pedicels. Fruit of 20 to 30 carpels, 

 arranged in a single ring round a broad, flat, central axis. 



In watery ditches, ponds, and edges of streams ; common in Europe, 

 temperate Asia, and North America, extending to the Arctic regions, 

 and reappearing in Australia. Abundant in Britain. FL att summer. 



2. A. ranunculoides, Linn. (fig. 975). Lesser W. The leaves and 

 peduncles form annual tufts, but will occasionally emit runners for a 

 succeeding year. Leaves narrow-lanceolate, or sometimes reduced to 

 a linear leafstalk. Flower-stems, in the ordinary state, simple, with a 

 single terminal umbel, or rarely a second whorl below it. Flowers 

 larger than in A. Plantago, sometimes near an inch diameter. Carpels 

 irregularly arranged in a globular head in the centre of the flower. 



In wet ditches and marshes, over the greater part of Europe, but 

 rare in the east. In Britain, as widely dispersed as A. Plantago, but 

 not near so frequent. Fl. summer and autumn. In var. repens the 

 flowering-stem bends down, and forms roots and leafy tufts at each 

 whorl of flowers. 



3. A. natans, Linn. (fig. 976). Floating W. Stems slender, and 

 floating on the surface of the water, producing at every node a tuft of 

 small ovate or oblong, stalked leaves, and 1 or 3 small flowers, whilst 

 the radical leaves of the original tuft are all reduced to a linear leaf- 

 stalk, scarcely dilated towards the top. Carpels in a globular head, 

 like those of A. ranunculoides, but much more pointed, and marked with 

 12 to 15 slender longitudinal ribs. 



In ponds and still waters, in western and some parts of central Europe. 

 In Britain very rare, and confined to western England, Wales, and west- 

 ern Ireland. [The subsolitary flowers, floating habit, and position of the 

 ovules, separate this from Alisma, under the name of Elisma, Buchenau.] 

 Fl. summer and autumn. 



