3G6 VARIOUS PLANT GROUPS 



(Figs. 39, 40, pages 49-51), gum arable 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, Ha;matoxy- 

 lon, Hymensea, Trachylobium, Pisum, Phaseolus, Rol)iiiia, Indigo- 

 fera, Glycyrrhiza, Astragalus, Arachis, and Leguniinosse. 



In their floral structure many acacias, like the gum arable 

 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 

 coaleseent. Stamens thus united are said to be monadel- 

 phous.^ The logwood-tree (Hamatoxylon), the courbaril- 

 tree (Hymensea) 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 

 coaleseent. Such an androecium is t(Tmed 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 



' I\Ion"a-dcrphous < Gr. monos, one; addpJios, a brother; meaning 

 in one brotherhood; indicated by the small i)arenthesis. 



- Pa-pil"i-on-a'ccous < L. papilio, a butterfly— from the resem- 

 blance. This is expressed in the formula by P"5+ j). 



^ Di"a-derphous < Gr. dis, two; FA^). 



* Gam"o-sep'al-ous < Gr. gamos, union; S'. 



5 Bi-la'bi-ate < L. bis, two; labium, lip; S5;. 



