FAMILIES OF FLOWERING PLANTS 22 
Fic. 190. The Yellow Gentian (Gentiana flavida Gray). After Britton and 
Brown, Ill. Fl. Northeast. U. S. 
rated from that family on account of their habit, their basal‘or alternate 
leaves, and the different position of the corolla-segments in the bud. 
There are 5 genera and about 35 species, widely distributed. The buck- 
bean (Menyanthes trifoliata) is a familiar denizen of our northern bogs ; 
it has a rather handsome spike of white flowers. Limnanthemum in- 
cludes a number of floating aquatics with leaves somewhat suggesting 
those of the water lily, and white or yellow flowers. L. nymphaeoides, 
of Europe, is occasionally cultivated for ornament. 
Family Apocynaceae. Dogbane Family. Consists of herbs shrubs, 
or in some tropical genera, trees, with an acrid and usually poisonous 
milky juice. The leaves are simple, and the flowers regular and 5-parted, 
the corolla often twisted, a fact which led Linnaeus to give the name 
Contortae to the group. The stamens are equal in number to the co- 
rolla-lobes, and inserted on the throat alternating with them ; the ovary 
is superior, 1-celled or with two distinct carpels; the fruit consists of 
two follicles, resembling those of milkweeds, or drupaceous. There are 
about 130 genera and 1,050 species in this widely distributed family. It 
is most abundantly represented, however, in tropical regions. The dog- 
banes are an important group, whether considered from the economic 
or other standpoint. As has been stated, their juice is ordinarily very 
poisonous ; but in some instances it has medicinal value, while in a few 
genera (Vahea and allies) it yields a fair quality of caoutchouc. A num- 
ber of important fiber plants are also contained in the family; and in a 
