CISTACEJE. (ROCK-ROSE FAMILY.) 45 



ORDER 16. CISTACE^E. (ROCK-ROSE FAMILY.) 



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

 indefinite stamens, a persistent calyx, a l-celled 3 - 5-valved pod with as many 

 parietal placenta? borne on the middle of the valves, and orthotropous albu- 

 minous seeds. Sepals 5 ; the two external small, like bracts, or sometimes 

 wanting ; the three others a little twisted in the bud. Petals 3 or 5, usu- 

 ally fugacious, 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 their apex. Em- 

 bryo 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. A small family : mostly of the Medi- 

 terranean region.) 



Synopsis. 



1. HELIANTHEMUM. Petals 5, crumpled in the bud, fugacious. Stamens and ovules nu- 



merous in the petal-bearing flowers. Style none. 



2. HUDSONIA. Petals 5, fugacious. Stamens 9-30. Style long and Blender. Pod strictly 



l-celled, 2-6-seeded. 



8. LECHEA. Petals 3, persistent. Stamens 3-12. Style none. Pod partly 3-celled, the 

 imperfect partitions bearing broad 2-seeded placentae. 



1. HEL.IANTHEMUM, Tburn. BOCK-ROSE. 



Petals 5, crumpled in the bud, fugacious. Stylo short or none : stigma 3- 

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

 ring. Flowers in most N. American species of two sorts, viz., 1. the primary, 

 or earliest ones, with large petals, indefinitely numerous stamens, and many- 

 seeded pods : 2. secondary, or later ones, which are much smaller and in clus- 

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

 pods. The yellow flowers open only once, in sunshine, and cast their petals by 

 the next day. (Name from rj\ios, the sun, and avQepov, flower.) 



1. H. Canaclense, Michx. (FROST-WEED.) Petal-bearing flowers soli- 

 tary ; the small secondary flowers clustered in the axils of the, leaves, nearly sessile ; 

 calyx of the large flowers hairy-pubescent ; of the small ones hoary, like the stem 

 and lower side of the lanceolate-oblong leaves. A variety is more hoary, and 

 with a stronger tendency to multiply the minute clustered flowers. Sandy or 

 gravelly dry soil, Maine to Wisconsin and southward, but rare west of the Alle- 

 ghanies. June -Aug. Stems at first simple. Corolla of the large flowers 1' 

 wide, producing pods 3" long : pods of the smaller flowers not larger than a 

 pin's head. Late in autumn, crystals of ice shoot from the cracked bark at the 

 root, whence the popular name. 



2. H. corymbosiim, Michx. Flowers all clustered at the summit of the 

 stem or branches, the petal-bearing ones at length on slender stalks; calyx 

 woolly. Pine barrens, New Jersey and southward along the coast. 



