FAMILIES OF FLOWERING PLANTS 179 
in the desert situations where it occurs, being covered at certain sea- 
sons with brilliant scarlet flowers. 
Family Cistaceae. Rock-rose Family. Contains four genera and 
about 160 species, natives almost exclusively of the northern hemis- 
phere, and abundant in both North America and Europe. They are 
shrubs or somewhat woody herbs, with simple leaves and solitary or 
clustered flowers, the latter regular. Sepals 3-5; petals 3-5 or wanting; 
stamens numerous; ovary 1-several-celled, capsular in fruit. Three 
genera are represented in North America. The pinweeds (Lechea) are 
small plants with insignificant fiowers and a wonderfully large number 
of species. The frostweeds (Helianthemum) have for the most part , 
rather showy yellow or white, but very evanescent flowers. Hudsonia 
contains 8 species of little heath-like plants with hoary foliage and 
starry yellow flowers (see Fig. 160). In Europe the species of Cistus 
are very numerous, and many of them have flowers of considerable size 
and‘beauty. C. Creticus yields the gum ladanum, used as a perfume, 
having a pleasant balsamic fragrance. C. ladaniferus in Spain and 
Portugal yields a similar product. 
