HYDEOCIIARIDACE.E. (FROG's-BIT FAMILY.) 441 



2. A IV AC II A HIS, Rich. (UD6RA, Nutt.) WATER-WEED. 



Flowers polygamo-diceciou*, solitary and sessile from a sessile and tubular 

 2-cleft axillary sputhe. Sterile flowers small or minute ; with 3 sepals, barely 

 united at the base, and usually 3 similar or narrower petals : filaments short and 

 monadelphous at the base, or none ; anthers 9, oval. Fertile flowers either pis- 

 tillate or apparently perfect: perianth extended into an extremely long and 

 capillary tube ; the limb 6-paited ; the small lobes (sepals and petals) obovate, 

 spreading. Stamens 3-G, sometimes merely short sterile filaments, without 

 anthers, or with imperfect ones, sometimes with oblong almost sessile anthers. 

 Ovary 1 -celled, with 3 parietal placentae, each bearing a few orthotropous ovules ; 

 the capillary style coherent with the tube of the perianth : stigmas 3, large, 2- 

 lobed or notched, exserted. Fruit oblong, coriaceous, few-seeded. Perennial 

 slender herbs, growing under water, with elongated branching stems, thickly 

 beset with pellucid arid veinless, 1-nerved, sessile, whorled or opposite leaves. 

 The staminate flowers (which are rarely seen) commonly break off, as in Val- 

 lisneria, and float on the surface, where they expand and shed their pollen 

 around the stigmas of the fertile flowers, which are raised to the surface by the 

 excessively prolonged calyx-tube, varying in length according to the depth of 

 the water. (Name formed of di>, throughout, and adapts, without charms, being 

 rather homely water- weeds.) 



1. A. CsHiaclensiS, Planchon. Leaves in threes or fours, or the lower 

 opposite, varying from linear to oval-oblong, obscurely and minutely serrulate ; 

 stigmas more or less 2-lobed. (Elodea Canadensis, Michx. Udora Canadensis, 

 Nutt. Anacharis Alsinastrum (Babingion), Nuttallii, and Canadensis (perhaps 

 also Chilensis), and also Apalanthe Schweinitzii, Planchon.) Slow streams 

 and ponds ; common. July. (Eu. ?) 



3. VAL,L,I]VERIA, Micheli. TAPE-GRASS.. EEL-GRASS. 



Flowers strictly dioecious : the sterile numerous and crowded in a head on a 

 conical receptacle, enclosed in an ovate at length 3-valved spathe which is borne 

 on a very short scape : stamens mostly 3. Fertile flowers solitary and sessile 

 in a tubular spathe which is borne on an exceedingly long scape. Perianth 

 (calyx) 3-parted in the sterile flowers; in the fertile with a linear tube. coherent 

 with the 1 -celled ovary, but not extended beyond it, 3-lobed (the lobes obovate) ; 

 also 3 linear small petals. Stigmas 3, large, nearly sessile, 2-lobed. Ovules 

 very numerous scattered over the walls, orthotropous ! Fruit elongated, cylin- 

 drical, berry-like. Stemless plants, with long and linear grass-like leaves, 

 growing entirely under water. The staminate clusters being confined to the 

 bottom of the water by the shortness of the scape, the flower-buds themselves 

 spontaneously break away from their short pedicels and float on the surface, 

 where they expand and shed their pollen around the fertile flowers, which are 

 raised to the surface at this time : afterwards the thread-form fertile scapes (2-4 

 feet long according to the depth of the water) coil up spirally and draw the ovary 

 under water to ripen. (Named in honor of Vallisneri, an early Italian botanist.) 



1. V. spiralis, L. Leaves linear, thin, long and ribbon-like (l-2 





