FAMILIES OF FLOWEKING PLANTS 179 



ill the desert situations where it occurs, being covered at certain sea- 

 sons with brilliant scarlet flowers. 



Famil}' 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 3 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. Creticiis yields the gum ladanum, used as a perfume, 

 having a pleasant balsamic fragrance. C. ladaniferus in Spain and 

 Portugal yields a similar product. 



