322 PICKEREL-WEED FAMILY. 



extremely long and slender scape : tube of the perianth not prolonged beyond 

 the 1-celIed ovary, with 3 obovate outer lobes (sepals) and 3 small inner 

 linear ones (petals),-and no stamens. Ovules very numerous lining the walls. 

 Stigmas 3, sessile, 2-lobed. Fruit cylindrical, berry-like. 



1. LIMNOBIUM, FROG'S-BIT. (Name in Greek means living in 

 pools.) Flowers whitish, the fertile ones larger, in summer. Jl 



L. Spongia. Floating free on still water S. & W. ; has been found in bays 

 of Lake Ontario : rooting copiously; leaves l'-2' long, purple beneath, tumid 

 at base with spongy air-cells. 



2. ANACHARIS, WATER-WEED. (Name from the Greek means 

 destitute of charms.) Fl. summer. ^ 



A. Canadensis. Slow streams and ponds : a rather homely weed, with 

 long branching stems, beset with pairs or whorls of pellucid and veinless 

 1-nerved minutely serrulate sessile leaves (^'-1' long), varying from linear 

 to ovate-oblong, the thread-like tube of the yellowish perianth often several 

 inches long. 



3. VALLISNEEIA, TAPE-GRASS, EEL-GRASS of fresh water. 

 (Named for A. Vallisneri, an early Italian botanist.) Fl. late summer, "il 



V. spirals. In clear ponds and slow streams, with bright green and grass- 

 like linear leaves (l°-2° long), delicately nerved and netted; fertile scapes 

 rising 2° - 4° long, according to the depth of the water, afterwards coiling up 

 spirally and drawing the fruit under water to ripen. — The leaves of this and 

 the preceding are excellent to show cyclosis. (See Structural Botany, p. 31, 

 Lessons, p. 167.) 



116. PONTEDERIACE-SI, PICKEREL-WEED F. 



A few water plants, distinguished from the foregoing by having 

 the tubular corolla-like perianth free from the ovary, and the flow- 

 ers perfect. Represented by 



Selldllera graminea, or Water Star-Grass ; a grass-like weed grow- 

 ing under water in streams, with branching stems beset with linear pellucid ses- 

 sile leaves ; the flower with a slender salver-form pale yellow perianth, of six 

 narrow equal divisions raised to the surface on a very slender tube, and only 3 

 stamens. 



Heteranth6ra renifdrmis, Mud-Plantain, in mud or shallow water 

 S. & W. ; with floating round-kidney-shaped leaves on long petioles, and 3-5 

 ephemeral white flowers, from the sheathing base or side of a petiole ; their per- 

 ianth salver-form, with a slender tube, bearing 6 nearly equal divisions and 3 

 dissimilar stamens, one with a greenish, two with yellow anthers. 



H. limdsa, in mud S. & W. : distinguished by its oblong or lance-oblong 

 leaves, and solitary blue flower. — The only widely common plant of the family 

 belongs to 



1. PONTEDERIA, Pickerel-weed. (Named for the Italian botanist 

 Pontedera.) Flowers in a terminal spike. Pei'ianth of 6 divisions irregularly 

 united below in a tube, the 3 most united forming an upper lip of 3 lobes, the 

 others more spreading and with more or less separate or lightl}' cohering 

 • claws fonning the lower lip, open only for a day, rolling up from the apex 

 downwards as it closes ; the 6-ribbed base thickening, turning green, and en- 

 closing the fruit. Stamens 6, the 3 lower in the throat, with incurved fila- 

 ments ; the 3 upper lower down and shorter, often imperfect. Ovary 3-celled, 

 2 cells empty, one with a hanging ovule. Fruit a 1-celled 1-secdcd utricle. 



P. cord^ta, Common P. Everywhere in shallow water ; stem l°-2°high, 

 naked below, above bearing a single j)etiolod heart-sliajjcil and oblong or lance- 

 arrow-shaped obtuse leaf, and a spike of ])urplisli-blue flowers ; upper lobe with 

 a conspicuous yellowish-green spot: fl. all summer, y. 



