NYMPHAEACEAE. 151 



Leaves cordate; flowers large, yellow. 187. Nymphaea, 151. 



Leaves peltate; flowers small, purple. 188. Brasenia, 151. 



187. NYMPHAEA. Yellow Pond Lilly. 



Acaulescent perennials from stout rootstocks, commonly 

 slightly milky ; leaves with united stipules which are sometimes 

 adnate to the base of the petioles; calyx more showy than the 

 corolla; sepals 5-12, concave, roundish, mostly yellow, and petal- 

 like; petals 10-20, hypogynous, small and thick, the innermost 

 or sometimes all of them stamen-like; stamens numerous, hy- 

 pogynous; stigmas radiate on the summit of the 10-25-celled 

 ovary; ovules and seeds numerous. 



Nymphaea polysepala (Engelm.) Greene. Wokas. Leaves orbicular or 

 broadly oval, deeply cordate, 20-30 cm. long, 12-20 cm. broad; calyx sub- 

 globose, about 8 cm. broad; sepals 8-12, yellow, often red-tinged; petals 12-18, 

 ovate-cuneate, truncate, 1-1.5 cm. long; stamens very numerous; fruit sub- 

 globose, 4-5 cm. long. 



Common in lakes. The seeds are used as food by some tribes of Indians 



188. BRASENIA. Watershield. 



Aquatic herbs with creeping rootstocks; leaves alternate, long- 

 petioled, centrally peltate, oval, floating; flowers axillary, small; 

 sepals 3 or 4; petals 3 or 4, linear, sessile; stamens 12-18; pistils 

 4-18, forming club-shaped indehiscent pods, each with 1-2 seeds. 



Brasenia schreberi Gmel. Watershield. Leaves alternate, long-petioled, 

 oval, entire or obscurely crenate, centrally peltate, 2-10 cm. long; flowers dull 

 purple; submerged parts of the plant coated with tough transparent jelly. 



Common in lakes. 



Family 41. CERATOPHYLLACEAE. Hornwort Family. 

 Aquatic herbs, with whorled finely dissected leaves; flowers 

 minute, sessile, monoecious, without calyx or corolla, but with 

 an 8-12-cleft involucre in place of a calyx. 



189. CERATOPHYLLUM. Hornwort. 



Herbs growing submerged; leaves sessile, cut into thrice- 

 forked, thread-like rigid divisions ; sterile flowers of 10-20 stamens ; 

 fruit an akene. 



Ceratophyllum demersum L. Stems 50-200 cm. long, sparingly branched; 

 leaves rigid, 8-25 mm. long; akene smooth, beaked with the persistent style 

 and having a sharp tubercle on each side at the base. 



Common in quiet streams and lakes. Very rarely found in flower or fruit. 



Family 42. RANUNCULACEAE. Buttercup Family. 

 Annual or perennial herbs, or sometimes woody plants, with 

 acrid sap ; leaves usually alternate (opposite in Clematis) , simple 



