832 coN"TRiBUTio]srs fkom the national herbarium. 



the name of palo Addn [Adam's tree]. When there is rain it sends forth a few 

 small leaves, but after a month it sheds them and remains naked all the year." 



107. CISTACEAE. Rock-rose Family. 



Kefekence : Grosser in Engl. Pflanzenreich IV. 193. 1903. 

 The only other genus represented in Mexico is Lechea, of which two species 

 occur. They are distinguished from Halimium by having 3 instead of 5 petals. 



1. HALIMIUM Spach, Ann. Sci. Nat. II. 6: 365. 1836. 



Plants herbaceous or sufErutescent, slender; leaves alternate, narrow, entire, 

 estipulate ; flowers racemose, subumbellate, paniciilate, or glomerate, all petalif- 

 erous or partly cleistogamous ; sepals 5, the 3 outer ones much narrower than 

 the others ; petals 5 in the petaliferous flowers, yellow, fugacious ; stamens 

 numerous; fruit a glabrous capsule, 3-valvate, many-seeded. 



The plants of this genus have usually been referred to Helianthemum, but 

 recent writers restrict that to certain Old World plants. 



Some of the United States species are known as frostweed and rock-rose. 

 They contain a volatile oil, tannin, and apparently a glucoside, having a bitter 

 and astringent taste and tonic and astringent properties. Formerly they were 

 employed as a remedy for diarrhea and scrofulous affections, and as a gargle 

 in the treatment of scarlatina. 



Leaves linear, mostly 1 to 3 cm. long, green. Flowers all petaliferous and 



pedicellate 1. H. aldersonii. 



Leaves broader or, if linear, less than 1 cm. long and grayish-pubescent. 



Stems hirsute or pilose with long spreading hairs 2. H. chihuahuense. 



Stems covered with a close, usually appressed, stellate pubescence. 



Pedicels of the petaliferous flowers much longer than those of the 

 cleistogamous flowers ; cleistogamous flowers sessile or nearly so. 



Leaves linear 3. H. argenteum. 



Leaves oblanceolate or broader. 



Sepals of the petaliferous flowers 3 to 4 mm. long ; leaves covered 



beneath with a dense grayish tonientum 4. H. glom.eratu.m. 



Sepals of the petaliferous flowers 5 to 6 mm. long; leaves green be- 

 neath, witli scattered stellate hairs 5. H. exaltatum. 



Pedicels all elongate, those of the two kinds of flowers subequal, or the 

 flowers sometimes all petaliferous. 

 Flowers subumbellate at the ends of the branches ; leaves mostly 5 to 



15 mm. wide 6. H. coulteri. 



Flowers scattered along the upper part of the branches, not umbel- 

 late ; leaves mostly 2 to 5 mm. ^vide. 

 Leaves oblanceolate-linear, broadest at the apex; flowers probably 



all petaliferous 7. H. nutans. 



Leaves mostly oblong or oblong-oblanceolate, broadest about the 

 middle ; flowers partly cleistogamous. 

 Pedicels about as long as the calyx ; stems simple below, strict. 



8. H. pringlei. 



Pedicels usually twice as long as the cal.vx ; stems usually branched 



below, weak 9. H. patens. 



1. Halimium aldersonii (Greene) Standi. 



Helianthemum aldersonii Greene, Erythea 1: 259. 1893. 



Dry hillsides, northern Baja California. Southern California, the t.ype from 

 San Diego County. 



Plants suffrutescent, 30 to 60 cm. high, with numerous erect branches ; leaves 

 sessile, 1 to 2 mm. wide, obscurely stellate-puberulent but green ; flowers all 



