366 VARIOUS PLANT GROUPS 
(Figs. 39, 40, pages 49-51), gum arabic tree (Fig. 156, 
page 164), tragacanth shrub (Fig. 157, page 165), licorice 
(Fig. 162, page 169), locust (Fig. 182, page 197), courbaril- 
tree and Zanzibar copal-tree (Fig. 273, page 289), indigo 
shrub (Fig. 275, page 293), and logwood-tree (Fig. 276, 
page 294). 
See on pages 408-411 the formulas given for Acacia, Hematoxy- 
lon, Hymenza, Trachylobium, Pisum, Phaseolus, Robinia, Indigo- 
fera, Glycyrrhiza, Astragalus, Arachis, and Leguminose. 
In their floral structure many acacias, like the gum arabic 
tree, approximate closely to certain members of the rose 
family, notably in the numerous stamens, and regular calyx 
and corolla. In some species the filaments are more or less 
coalescent. Stamens thus united are said to be monadel- 
phous. The logwood-tree (Hematoxylon), the courbaril- 
tree (Hymenzea) and the Zanzibar copal-tree (Trachylobium) 
present irregular corollas, with the peculiarity that the 
uppermost petal is at first enfolded by the side ones, and 
these in turn by the lower pair. A large majority of the 
family, represented by peas (Pisum), beans (Phaseolus), and 
the other examples referred to, have what is called a papil- 
ionaceous 2 corolla. This consists of five petals: one com- 
paratively large called the standard, which is above the others 
and enfolds them in the bud; two side ones called the wings; 
and two lower ones grown together to form what is called the 
keel. A curious condition of the androecium commonly found 
with the papilionaceous corolla is that there is one uppermost 
stamen free from the other nine which are more or less 
coalescent. Such an androecium is termed diadelphous.* 
Another peculiarity usually accompanying the papilionaceous 
corolla is the irregularity and coalescence of the sepals to 
form a calyx described as gamosepalous ‘ and bilabiate,® that 
1 Mon’’a-del’phous < Gr. monos, one; adelphos, a brother; meaning 
in one brotherhood; indicated by the small parenthesis. 
2 Pa-pil’’i-on-a’/ceous < L. papilio, a butterfly—from the resem- 
blance. This is expressed in the formula by P’’z}>). 
3 Di’’a-del’phous < Gr. dis, two; FA%). 
4 Gam/’o-sep’al-ous < Gr. gamos, union; 9). 
5 Bi-la’bi-ate < L. bis, two; labiwm, lip; S$). 
