54 FLORA. 



i. ALISMA L. 



Perennial or rarely annual herbs with erect or floating leaves, the blades several- 

 ribbed, the ribs connected by transverse veinlets, or seemingly pinnately veined. 

 Scapes short or elongated. Inflorescence paniculate or umbellate-paniculate. 

 Flowers small, numerous on unequal 3-bracteolate pedicels, the petals white or 

 rose-tinted. Stamens 6 or 9, subperigynous. Ovaries few or many, borne in one 

 or several whorls, ripening into flattened achenes which are 2-3 -ribbed on the 

 curved back and i-2-ribbed on the sides. [Greek, said to be in reference to the 

 occurrence of the typical species in saline situations.] About 10 species, widely 

 distributed in temperate and tropical regions. The following are known to occur 

 in eastern N. Am. 



Stamens 6, strongly compressed ; flowers panicled. i. A. Plant ago-aquatica. 



Stamens 9, turgid ; flowers umbelled. 2. A. tenellum. 



1. Alisma Plantago-aquatica L. WATER PLANTAIN. (I. F. f. 188.) 

 Leaves ovate, acute at the apex, cordate, rounded or narrowed at the base, the 

 blades 3-io-ribbed; petioles 2-25 cm. long; scapes occasionally 2 from the same 

 root, usually solitary, 0.2-1.3 m. high; inflorescence a large loose panicle ; pedicels 

 verticillate in 3's-io's, subtended by 3 striate acuminate bracts; petals 1-2 mm. 

 long; styles deciduous, the base remaining as a small point or short beak on the 

 inner curve of the achene; stigma small, terminal; achenes obliquely obovate, 

 nearly 2 mm. long, arranged in a circle, forming an obtusely triangular truncate 

 head. In shallow water or mud throughout N. Am. Also in Europe and Asia. 

 June-Sept. 



2. Alisma tenellum Mart. DWARF WATER PLANTAIN. (I. F. f. 189.) Plant 

 delicate, stoloniferous, 2-12 cm. high. Leaves lanceolate or linear-lanceolate, the 

 blades acute at both ends, 6-30 mm. long, 2-6 mm. wide ; petioles longer or shorter 

 than the blades, narrowly dilated at the base; scape solitary, often surpassing the 

 leaves, commonly reclined; umbel 2-8-flowered; pedicels very unequal, often 

 recurved in fruit ; bracts lanceolate, more or less connate at the base; flowers white; 

 stamens 9; style much shorter than the ovary; ovaries numerous; achenes in sev- 

 eral whorls, coriaceous, turgid, obovate, not I mm. long, enclosed by the erect per- 

 sistent sepals, the beak short, sharp. In mud, Mass, to W. Ont. and Minn., south 

 to Fla., Mo., and Tex. April-Aug. 



2. ECHINODORUS Rich. 



Perennial or annual herbs with long-petioled elliptic, ovate or lanceolate, often 

 cordate or sagittate leaves, 3~9-ribbed and mostly punctuate with dots or lines. 

 Scapes often longer than the leaves; inflorescence racemose or paniculate, the 

 flowers verticillate, each verticil with 3 outer bracts and numerous inner bracteoles; 

 flowers perfect; sepals 3, distinct, persistent; petals white, deciduous; receptacle 

 large, convex or globose; stamens 12-30; ovaries numerous; style obliquely api- 

 cal, persistent; stigma simple; fruit achenes. more or less compressed, coriaceous, 

 ribbed and beaked, forming spinose heads. [Greek, in allusion to the spinose 

 heads of fruit.] About 14 species, mostly natives of America. Only the follow- 

 ing are known in N. Am. : 



Scapes reclining or prostrate; style shorter than the ovary ; beak of achene short. 



i. E, radicans. 

 Scapes erect; style longer than the ovary; beak of achene long. 2. E. cordifolitis. 



i. Echinodorus radicans (Nutt.) Engelm. CREEPING BUR-HEAD. (I. F. 

 f. 190.) Leaves coarse, ovate, obtuse, cordate, 5-20 cm. long, 3-18 cm. wide, marked 

 with short pellucid lines, the nerves 5-9, connected by netted cross-veins. Petioles 

 sometimes 0.5 m. long; scapes creeping, 0.6- 1. 4m. long, slightly scabrous, often root- 

 ing at the nodes; verticils distant; pedicels 3-12, unequal, slender or filiform; sepals 

 persistent, much shorter than the heads; petals larger, obovate, about 6 mm. long; 

 stamens about 20; style shorter than the ovary; achenes numerous, about 4 mm. 

 long, 6-io-ribbed, with 2-several oval glands on each side and beaks about one- 



