212 EVOLUTION OF PLANTS 
eral native species of Aralia, including the ginseng, may 
be mentioned. The Umbellifere are mainly inhabitants 
of the northern hemisphere and are all closely related. 
Both of these families are distinguished by the arrange- 
ment of their usually inconspicuous flowers in umbels 
—hence they are united with the allied family Corna- 
cee (dogwoods) into a common order Umbelliflore. 
Two of the most specialized orders are the Passi- 
florine (passion-flowers and their allies) and the Cac- 
taceee. The latter is a very peculiar group of American 
desert plants; the former are also largely American, 
but belong principally to the moist tropical regions. 
The last order of the Calyciflore is a very important 
one, the Leguminose, including the beans, peas (Fig. 
51, F, G), and other leguminous plants. Of the three 
families, two, the Mimosez, of which various species of 
Acacia and Mimosa are cultivated, and the Cesalpineex, 
of which the honey-locust (Gleditschia) and the red-bud 
(Cercis) may be mentioned as native, are mainly tropi- 
eal, while the other and much larger family, Papiliona- 
cez, includes most of the numerous Leguminose of 
temperate regions. The characteristic butterfly-shaped 
flowers of these plants, and their pod-shaped fruits, are 
too familiar to need further description. 
THE SYMPETALZE 
The Dicotyledons which have just been considered 
either have the petals entirely separate or quite absent. 
There is a second division, including the most specialized 
as well as the larger number of the Dicotyledons, in 
which with very few exceptions the petals are more or 
