FAMILIES OF FLOWEEING PLANTS 



121 



sented by a single species extending throughout the eastern half of the 

 United States. The plants are fresh-water aquatic herbs, exhibiting a 

 primitive type of structure, with little differentiation between leaf and 

 stem. The flowers are without any perianth, and are enveloped at first 

 in a spathe-like involucre. The ovary is -frequently stipitate (stalked), 

 becoming a capsule in fruit (see Fig. 105). 



Family Hydrostachydaceae. Hydrostachys Family. A group of 

 aciuatic plants, consisting of the single genus Hydrostachys, closely re- 

 lated to the preceding family. 



Family Crassulaceae. Or- 

 pine Family. This interest- 

 ing group of plants, of wide 

 geographic distribution, com- 

 prises about 15 genera and 

 over 500 species. Thej are 

 herbs or half-shrubs, remark- 

 able for their fleshy or succu- 

 lent herbage, the result of 

 adaptation to the arid situa- 

 tions in which many of them 

 are found. The persistent 

 calyx is 4-5-parted; the petals, 

 equal in number, are also per- 

 sistent; stamens and carpels 

 equalling the petals; the car- 

 pels either whollj' distinct or 

 slightly united below, becom- 

 ing small follicles in fruit. 



Sedum, the stone-crops, 

 includes many North Ameri- 

 can species. The American 

 orpine or live-for-ever {Sedum 

 felephioides) is one of the most 

 attractive, with the light green 

 foliage and clusters of pink 

 floAvers (see Fig. 106). A Eu- 

 ropean species {Sedum acre) having bright yellow flowers, is frequently 

 seen in cultivation. In southern Europe and northern Africa species 

 of Echeueria and Sempervivum are very common, growing frequently on 

 the roofs of houses and on old walls. 



Family Saxifragaceae. Saxifrage Family. Contains about 70 gen- 

 era and 600 species, natives mainly of temperate regions, many being 

 alpine. They are herbs, shrubs, or even trees, with solitary or vari- 



Fig. io6. The American orpine (Si\iiiin ielephioides) 

 with detached flower enlarged. Original. 



