136 FAMILIES OF FLOWERING PLANTS 
hiscent (not splitting open) at maturity, is one-seeded, and structurally 
a pod. The genus was formerly placed with the Polygalaceae, and by 
many authors is now regarded as a distinct family. 
Family Papilionaceae. Pea Family. This, the typical group of 
the Leguminosae, is at the same time the largest and most important 
family of the Order Rosales. The plants range in size from the small- 
est of herbs to the loftiest of forest trees, and are comprised in about 
310 genera and 5000 species, most abundant in tropical and subtropical 
regions, though some extend to the Arctic zone. The character from 
From Coulter’s Plant Structures. Copyright, 1900, D. Appleton & Co. 
Fig. 119. A leguminous plant (Lotus) showing flowering branch; (1), detached flower; (2), clus- 
ters of 10 stamens; (3), single carpel; (4), fruit, a pod; (5), petals dissected apart; (6), consisting of 
standard (a); wings (5); and keel (c); and floral diagram (7). After Wossidlo. 
which the family takes its name is found in the peculiar and very irreg- 
ular shape of the flower (see Fig. 119). The upper petal, usually the 
largest, is known as the banner or standard; the two lateral are called 
‘wings, and the lowermost or forward pair jointly form the keel, which 
usually closely enfolds and protects the stamens and pistil. The lat- 
ter is 1-celled, forming a pod in fruit. The stamens are usually 10, and 
may be distinct, diadelphous (united into two sets by their filaments, 
or monadelphous (similarly united into a single set). 
The papilionaceous flower, as it is usually called, is in most of the 
genera identifiable at sight, but there are some exceptions; thus in 
Amorpha the corolla consists of only one petal, the standard, which is 
folded over the pistil like the keel in an ordinary flower. So also the 
