CERATOPHYLL^. 139 



2. M. hippuroides, Nutt. Stems 48 in. long, growing in mud or 

 shallow water, the emersed branches erect, simple, leafy, flowering through- 

 out: submersed leaves in whorls of 4 and 6, with 68 pairs of capillary 

 pinnae; emersed ones often alternate, linear-lanceolate, serrate or dentate, 

 or the uppermost entire; the lowest often pinnatifid: petals often 

 pinkish and somewhat persistent : stamens 4 : carpels carinate and some- 

 what roughened; deep grooves between them. In Marin Co., also on 

 the lower San Joaquin. June Sept. 



3. CALLITBICHE, Columna. Small and slender, growing in water 

 or on moist shaded ground. Leaves opposite, linear, spatulate or 

 obovate. Flowers solitary in the axils, subtended by a pair of falcate or 

 lunate membranous bracts, mostly consisting of a single stamen and 

 pistil. Filaments elongated: anthers reniform, the cells ultimately 

 confluent. Styles 2, filiform, papillose. Fruit sessile or peduncled, 

 4-celled, more or less carinate or winged on the margins, 4-lobed, the 

 lobes united in pairs, forming 2 discs with a groove between them, at 

 maturity parting into 4 compressed carpels, each 1-seeded. 



1. C. margiuata, Torr. Usually terrestrial and very small; when 

 aquatic the submersed leaves linear, 1-nerved, passing gradually into 

 the emersed, which are oblanceolate or spatulate, 3-nerved: styles 

 elongated, reflexed, deciduous: mature fruit on slender pedicels, often 

 buried in the mud, deeply emarginate at both ends, broader than high, the 

 margins of the thick carpels widely divergent and narrowly winged. 

 Low grounds, among growing grain, etc., from San Mateo and Alameda 

 counties northward. June. 



2. C. palustris, L. Usually aquatic, with linear retuse or bifid 

 submersed leaves, and spatulate or obovate emersed ones, these rounded 

 or truncate or retuse at apex, narrowed into a margined petiole, and 

 profusely dotted with stellate scales: fr. sessile, oblong, with a small 

 apical notch, narrow- winged above, deeply grooved between the lobes. 

 In sluggish or stagnant shallow pools. June. 



OBDEB XLIII. CERATOPHYLL/E. 



Represented by a single species of the genus 



1. CERATOPHYLLUM, Linn. (HOBNWOBT). Aquatic herbs, with 

 rigid verticillate leaves, these usually pinnatifid and the segments 

 toothed. Flowers clustered in the leaf -axils, involucrate, unisexual. 

 Involucre multifid. Calyx and corolla wanting. Stamens 1420. Ovary 

 ovate, 1-celled; style filiform, incurved. Fruit a small nutlet: the seed 

 pendulous. Albumen 0; cotyledons 4, verticillate, 2 larger than the 

 others; plumule conspicuous, compound. 



1. C. demersum, L. Stem 1 2 ft. long, nearly glabrous; in ternodes 

 short; leaves in whorls of 6 or 8; the linear segments acute, aculeate- 



