FAMILIES OF FLOWERING 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 
aquatic 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. They 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 wholly 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 
telephioides) is one of the most 
attractive, with the light green 
foliage and clusters of pink 
flowers (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 Echeveria 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. 106. The American orpine (Sedum telephioides) 
with detached flower enlarged. Original. 
