898 THE CALLITRICHE FAMILY. [CaUitriche. 



oblong, 1 to 6 lines long, or the lower submerged ones narrow-linear, and 

 obtuse or notched at the top ; the upper ones obovate, and spreading 

 in little tufts on the surface of the water, or all submerged and linear. 

 Flowers minute, usually solitary in each axil, between 2 minute bracts vary- 

 ing much in size and sometimes wholly wanting. Male flowers consisting 

 of a single stamen with a conspicuous filament ; the females of a sessile 

 or stalked ovary, with 2 erect or recurved styles. Fruit from to 1 line 

 in diameter, the lobes either rounded or keeled or winged on the edge. 

 In shallow waters or wet mud, dispersed all over the globe. Abund- 

 ant in Britain. Fl. the whole season. It has been variously divided into 

 from 2 to about 20 supposed species, from slight differences in the size 

 and form of the fruits, the direction of the styles, in the bracts, &c., or 

 from the presence or absence of the upper obovate leaves ; but the 

 distinctive characters which have been given all fail when applied to a 

 large number of specimens collected in different parts of the world. 

 [The British forms generally recognised as species or varieties are six, 

 of which the first five have usually floating leaves, bracteate flowers, 

 and the fruit-lobes broadly connate. 



a. C. verna, Linn, (aquatica, Sm.). Fruit subsessile, its lobes turgid, 

 sharply keeled. 



b. C. platycarpa, Kuetz. Fruit large, subsessile, its lobes flattish, 

 sharply keeled. Often grows prostrate on mud, and is the 0. stagnates, 

 Scop. 



c. C. hamulata, Kuetz. Fruit subsessile, its lobes flattish, shortly 

 broadly keeled. 



d. 0. obtusangula, Lag. Fruit subsessile, its lobes turgid, back 

 obtusely trigonous. 



e. C. pedunculata, DC. Leaves linear. Fruit sessile or stalked, its 

 lobes flattish, sharply keeled. 



f. G. autumnalis, Linn. Leaves all submerged and linear, truncate. 

 Fruit larger, stalked or sessile, its lobes keeled or winged, connate only 

 at the axis. Eare and local.] 



LXXI. URTICACEJE. THE NETTLE FAMILY. 



Herbs, or, in exotic genera, trees or shrubs, with leaves 

 usually rough or stinging, more or less conspicuous stipules, and 

 small, herbaceous, unisexual flowers. Perianth in the males 

 regular and simple. Stamens as many as segments of the peri- 

 anth and opposite to them, or rarely fewer. Perianth of the 

 females often less divided. Ovary free or rarely adherent to 

 the perianth, with a single ovule, and 1 or 2 styles or stigmas. 

 Fruit small, 1 -seeded, dry or rarely succulent. Seed with or 

 without albumen, the radicle pointing upwards. 



A very large Order, chiefly tropical, of which the few British species 

 give a very inadequate idea. It is readily distinguished from Euphor- 

 Uacece by the single-seeded fruit, from Amentacece by the regular perianth 

 of the male flowers. 



