VOL. II.] 



ROCK-ROSE FAMILY. 



439 



Family 78. CISTACEAE Lindl. Nat. Syst. Ed. 2, 91. 1836. 



ROCK-ROSE FAMILY. 



Shrubs or low woody herbs, with alternate or opposite simple leaves, and 

 solitary racemose clustered or paniculate flowers. Flowers regular, generally 

 perfect. Sepals 3-5, persistent, when 5 the 2 exterior ones smaller and bract- 

 like, the 3 inner convolute. Petals 5 or 3, or sometimes wanting, fugacious. 

 Stamens oo, hypogynous. Ovary i, sessile, i -several-celled; ovules orthotro- 

 pous, stalked; style simple; stigma entire or 3-lobed. Capsule dehiscent by 

 valves. Seeds several or numerous; embryo slender, straight or curved; endo- 

 sperm starchy or fleshy. 



Four genera and about 160 species, all but i or 2 natives of the northern hemisphere. 



Petals 5, yellow, fugacious, or wanting. 



Leaves broad, lanceolate or oblong. I. Helianthemum. 



Leaves subulate or scale-like, imbricated; style long. 2. Hudsonia. 



Petals 3, not yellow, persistent; flowers minute; style none. 3. Lechea. 



i. HELIANTHEMUM Pers. Syn. 2: 75. 1807. 



Woody herbs or low shrubs, more or less branching, mostly with showy yellow flowers, 

 and sometimes (in the following species) with other smaller apetalous ones. Petals in the 

 larger flowers large, fugacious. Stamens numerous. Placentae or false septa 3. Ovules 

 few or oo ; style short, or filiform, or club-shaped, jointed with the ovary; stigma capitate or 

 3-lobed. Embryo curved. [Greek, sun-flower.] 



About 125 species, natives of North and Central America, the Mediterranean region, India, and 

 a few in South America. Besides the following, about 8 others occur in the Southern States and on 

 the Pacific Coast. Some of the species are known as Rock-rose or Sun-rose. 



Petaliferous flowers solitary, few or several; apetalous flowers in axillary sessile clusters. 



Petaliferous flowers 5-12, in a short terminal cymose raceme, their capsules i ^"-2" long, little, 

 if at all, overtopped by the short later axillary branches; capsules of the apetalous flowers 

 about i" in diameter. I. ff. majus. 



Petaliferous flowers solitary, rarely 2, their capsules 3"~4" long, much overtopped by the later 

 elongated axillary branches; capsules of the apetalous flowers nearly 2" in diameter. 



2. H. Canadense. 

 Flowers all cymose at the summit of the stem, the petaliferous ones slender-pedicelled. 



3. H. corymbosum. 



i. Helianthemum majus (L.) B.S.P. Hoary Frost weed. (Fig. 2470.) 



Lechea major L. Sp. PI. 90. 1753. 



Helianlhemum majus B.S.P. Prel. Cat. N. Y. 6. 1888. 



Hoary-canescent, stem erect, i-2 high, at first 

 simple, later with numerous short ascending branch- 

 es. Leaves oblong-lanceolate or oblanceolate, acute 

 or obtuse, S^-iS" long, stellate-canescent beneath, 

 darker above, short-petioled; petaliferous flowers 

 5-12 in a terminal cymose raceme, their corollas 

 7 // -i2 // broad, light yellow, their sepals densely 

 canescent, the outer nearly as long as the inner, 

 their capsules ovoid, i^"-2" long, little if at all 

 overtopped by the later axillary branches; apetalous 

 flowers appearing later, minute, clustered in the 

 axils, nearly sessile, their capsules about i" in di- 

 ameter; seeds evenly reticulated. 



In dry soil, Maine to Minnesota and South Dakota, 

 south to North Carolina and Texas. Petaliferous 

 flowers June-July. 



