CERATOPHYLLACEAB (HORNWOET FAMILY) 889 



preceding ; stigma-lobes a fourth to a tliird as long as the style ; anthers shorty 

 almost spherical; seeds roughened. — Prairies, Ind., Wise, and e. Minn. 



4. T. calycinum Engelm. Larger ; petals usually 8-10 ; stamens 30 or more 

 — Sandy soil or rocks, s. Mo. {Blankinship) to Neb. and southwestw. 



4. PORTULACA [Tourn.] L. Purslane 



Calyx 2-cleft ; the tube cohering with the ovary below. Petals 5, rarely 6, 

 inserted on the calyx with the 7-20 stamens, fugacious. Style mostly 3-8- 

 parted. Pod 1-celled, globular, many-seeded, opening transversely, the upper 

 part (with the upper part of the calyx) separating as a lid. — Flesliy annuals, 

 with mostly scattered leaves. (An old Latin name, of unknown meaning.) 



1. P. olekAcea L. (Common P.) Prosft'oJe, very smooth ; leaves ohovate 

 or wedge-form ; flowers sessile (opening only in sunny mornings) ; sepals keeled ; 

 petals pale yellow ; stamens 7-12 ; style deeply 5-6-parted ; flower-bud flat and 

 acute. — Cultivated and waste grounds ; common. — Seemingly indigenous westw. 

 and southwestw. (Nat. from Eu.) 



2. P. negl^cta Mackenzie & Bush, known to us from description only, appears 

 to be a more luxuriant plant with ascending stems, larger leaves (2.6-5 cm. 

 long, 1.2-2.5 cm. broad), and more numerous (15-18) stamejis. — Rich bottom 

 lands, Mo. and Kan. 



3. P. retiisa Engelm . Leaves often retuse ; calyx-lobes obtuse in the bud ; 

 petals small or minute ; style shorter, S-i-clefl ; seeds larger, sharply tubercu- 

 late ; otherwise like P. oleracea. — Ark. to Tex. and westw. ; reported from 

 Kan., la., and Minn. 



4. P. pilbsa L. Ascending or spreading, copiously hairy in the axils ; leaves 

 linear-subulate, nearly terete, 6-12 mm. long ; petals red or purple. — Barrens, 

 Mo. and Kan. to Tex., etc. 



CERATOPHYLLAcEAE (Hornwort Pamilt) 



Aquatic herbs, with whorled finely dissected leaves, and minute axillary and 

 sessile monoecious flowers without floral envelopes, but with anS-12-cleft invo- 

 lucre in place of a calyx, the fertile a simple 1-celled ovary, with a suspended 

 orthotropous ovule ; seed fllled by a highly developed embryo with a very shor\, 

 radicle, thick oval cotyledons, and a plumule consisting of several nodes and 

 leaves. — Consists only of the genus 



1. CERATOPHYLLUM L. Hornwort 



Sterile flowers of 10-20 stamens, with large sessile anthers. Fruit an aohene, 

 beaked with the slender persistent style. — Herbs growing under water ; the 

 sessile leaves cut into thrice-forked thread-like rigid divisions (whence the 

 name from K^pas, a horn, and (piWov, leaf). 



1. C. demfirsum L. Fruit smooth, marginless, beaked with a long persistent 

 style, and with a short spine or tubercle at the base on each side. — Slow streams 

 and ponds, across the continent. (Eu., etc.) Var. echinXtum Gray has the 

 fruit mostly larger (6 mm. long), rough-pimpled on the sides, the narrowly 

 winged margin spiny-toothed. — Similar range. 



NYMPHAEACEAE (Water Lilt Family) 



Aquatic perennial herbs, with horizontal rootstocks and peltate or sometimes 

 only cordate leaves floating or emersed; the ovules borne on the sides or back 

 {or when solitary hanging from the summit) of the cells, not on the ventral 



