576 CISTACEAE (ROCKROSE FAMILY) 



1. ELATINE L. WATERWORT 



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

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

 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 and 

 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. triandra 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. brachyspe'rma 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. BERGIA L. 



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

 5. Stamens 5 or JO. 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. ni. to Kan., south w. and westw. 



CISTACEAE (ROCKROSE FAMILY) 



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

 indefinite stamens, a persistent calyx, a \-celled 3-5-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, bract-like, or sometimes 

 wanting ; 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 

 stalks, 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). Stigma nearly sessile. 



Stamens and ovules numerous In the petal-bearing flowers. 



2. Hudsonia. Petals 5, fugacious. Stamens 9-30. Style long and slender. Pod strictly l-elled, 



2-6-seeded. Heath-like. 



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

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



1. HELIANTHEMUM [Tourn.] Mill. ROCKROSE 



Capsule strictly 1-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 



