576 CISTACEAE (^ROCKROSE FAMILY) 



1. ELATtNE L. Watebwort 



Sepals 2-4, obtuse. Petals 2-4, hypogynous. Stamens as many, rarely twice 



as many. Styles, or sessile capitate stigmas, 2-4. Pod membranaceous, 2-4- 

 celled, several-many-seeded, 2-4-valved ; the partitions left attached to the axis, 

 or evanescent. — Dwarf plants, often rooting at the nodes. (A Greek name for 

 an obscure herb.) 



1. E. americana (Pursh) Arn. Tufted, 1-2.5 cm. high, creeping; leaves 

 obovate, obtuse, 2-6 mm. long; flowers sessile, rarely opening in the aquatie 

 form ; sepals, petals, stamens, and stigmas 2, rarely 3 ; seeds 5 or 6 in each cell, 

 rising from the base, relatively large, marked by 9 or 10 longitudinal lines anC- 

 20-30 crossbars.— Margin of ponds, etc., e. Que. to B. C, s. to Va., Mo., and 

 In the Rocky Mts. to Mex. 



2. E. triindra Schkuhr. Leaves oblanceolate or nearly lanceolate; petals 

 and stamens commonly 3 ; seeds more slender, covering the axis. — Ponds, 111. 

 to Neb., and westw. (Eu.) 



3. E. brachysp6rma Gray. Leaves oblong or oval, with narrowed base; 

 flowers mostly dimerous ; seeds short-oblong, with 6 or 7 longitudinal lines and 

 10-12 crossbars. — 111. and south westw. 



2. BliJRGIA L. 



Sepals 5, acuminate, with thickened midnerve and scarious margins. Petals 

 5. Stamens 5 or 10. Pod of firm texture. — Diffuse or ascending plants, chiefly 

 tropical. (Named for P. J. Bergius, a Swedish botanist of the 18th century.) 



1. B. texana (Hook.) Seubert. Branched from the base , branches 1-4 dm. 

 long ; flowers scarcely peduncled in the axils of the lance-oblong serrulate 

 leaves. — Swamps and wet banks, s. 111. to Kan., southw. and westw. 



CISTACEAE (Rockrose Family) 



Low shrubs or herbs, with regular flowers, distinct and hypogynous mostly 

 indefinite stamens, a persistent calyx, a l-celled o-d-valved capsule with as many 

 parietal placentae borne on the middle of the valves, and orthotropous albumi- 

 nous seeds. Sepals 5 ; the two external much smaller, bra-ct-like, or sometimes 

 warning ; the 3 others a little twisted in the bud. Petals 3 or 5, convolute in 

 the opposite direction from the calyx in the bud. Anthers short, innate, on 

 slender filaments. Style single or none. Ovules few or many, on slender 

 <}talks, with the orifice at the apex. Embryo long and slender, straightish or 

 curved, in mealy albumen ; cotyledons narrow. Leaves simple and mostly 

 entire, the lower usually opposite, and the upper alternate. — Inert plants. 



1. Helianthemum. Petals 5, crumpled in the bud, fugacious (or none). Stignia nearly sessile. 



Stamens and ovules numerous in the petal-bearing flowers. 



2. Hudsonia. Petals 5, fugacious. Stamens 9-80. Style long and slender. Pod strictly l-celled, 



2-(;-seeded. Heath-like. 

 8. Lechea. Petals 3, flat in the bud, withering-persistent. Stamens 8-12. Style none. Pod 

 partly 3-celled, the imperfect partitions bearing broad 2-seeded placentae. 



1. HELIANTHEMUBir [Tourn.] Mill. Rockrose 



Capsule strictly l-celled. Embryo curved in the form of a hook or ring. 

 Flowers in most N. American species of two sorts, viz., primary or earlier 

 ones, with large yellow petals, indefinitely numerous stamens, and many-seeded 

 pods ; and secondary, or later ones, which are much smaller and in clusters, 

 with small petals or none, 3-10 stamens, and much smaller 3-few-seeded pods. 



