within, its upper lip obcordate; ovary surrounded by a slenderly 10- to 12-toothed 

 disk: capsule ovoid, acute, about 5 mm. long. Hydrotrida caroliniana (Walt.) 

 Small. 



On margins of ponds and streams, in swamps, forming mats in water, and in 

 bogs in pinelands in e. Tex., May-Oct.; from Fla. to Tex., n. to Va. 



3. Bacopa rotundifolia (Michx. ) Wettst. Disc water-hyssop. Fig. 683. 



Plant creeping, with elongate and lax terminally pubescent branches to 6 dm. 

 long, forming mats on mud or attached and floating; leaves thin, suborbicular to 

 broadly obovate, with subcuneately narrowed but clasping bases, clearly palmately 

 many-nerved, the larger ones to 35 mm. long and 25 mm. wide; flowers usually 

 2 to 4 from upper nodes; pedicels 2 or 3 times as long as calyx, slender, pubescent, 

 to 2 cm. long; outer sepals ovate, 6-8 mm. long; corolla exserted, campanulate, 

 6-10 mm. long, the wide-spreading limb about as broad, white, with yellow throat; 

 capsule globose to subglobose, about as long as sepals. Macuillamia rotundifolia 

 (Michx.) Raf. 



In mud and water in and about lakes, pools, ditches and ponds in Okla. 

 (McCurtain, Johnston, Washington and Comanche cos.), throughout Tex. and 

 Ariz. (Maricopa Co.), May-Nov.; from Miss, to Tex. and Ariz., n. to Ind., 111., 

 Minn., N.D. and Mont. 



2. Limosella L. Mudwort 



Small rosulate plants of aquatic or wet habitats, usually acaulescent; leaves 

 basal, erect, rarely cauline; flowers solitary on naked 1 -flowered scapes, white 

 to pink or pale-blue; calyx campanulate; corolla campanulate, nearly regular, 

 the upper surface of petals minutely to sparsely papillate; stamens 4; style 

 terminal or subterminal; capsule globose to ellipsoid, 2-celled by a very thin 

 partition, many-seeded. 



About 15 cosmopolitan species. 



An Arizona species, L. piihli flora Penn., known only from the type collection 

 (Cochise Co.) has oblanceolate leaves attenuate at base, obtuse puberulent corolla 

 lobes, globose-ovoid capsules, and seeds a little longer than wide. 



1. Leaves linear to linear-spatulate, 2 mm. wide or less; corolla lobes rounded; 

 style 0.5-1 mm. long, straight or arcuately curved 1. L. acaulis. 



1. Leaves with an elliptic-oblong blade and long petiole, 2-8 mm. wide; corolla 

 lobes acute; style 0.2-0.4 mm. long, usually sharply decurved at 

 base 2. L. aquatica. 



1. Limosella acaulis Ses. & Mo?. Fig. 684. 



Cespitose, stoloniferous plants, often forming mats; leaves flat, linear to 

 linear-spatulate, 1-6 cm. long, the stipules somewhat auriculate; flowers solitary 

 on erect scapes; calyx campanulate; corolla nearly regular, white; petals oblong, 

 rounded, sparsely papillate on inner face; stamens 4; style 0.2-0.7 mm. long, 

 equal to or shorter than ovary; capsule ovoid, about 3 mm. long, 2-celIed by a 

 thin partition; seeds many, ridged and reticulate. 



Margins of ponds, lakes and streams, often in shallow water, in N. M. (Catron, 

 Mora and Sandoval cos.) and Ariz. (Apache, Coconino and Santa Cruz cos.), 

 June-Oct.; N.M., Ariz., Calif, and Mex. 



2. Limosella aquatica L. Fig. 685. 



Tufted annual 5-12 cm. tall, from threadlike rhizomes or stolons, rooting 

 at nodes; leaves on long slender petioles, 3-10 cm. long, the blades from linear- 

 spatulate to broadly oblong-elliptic, 1-3 cm. long, 3-12 mm. wide, with broad 

 sheathing base and conspicuous hyaline stipules; peduncles shorter than leaves, 



1461 



