410 EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



(Ex., the Pea, Bean, Locust, Clover, &c.) The vexillum is the 

 largest petal, and external in aestivation, in all true papilionaceous 

 corollas, as in the diagram, Fig. 382. But in the 



770. Sllbord, CaesalpineiB (to which Cassia, Cercis, and the Honey- 

 Locust belong), the corolla gradually loses its papilionaceous char- 

 acter, and always has the vexillum, or superior petal, covered by 

 the lateral ones in sestivation ; the stamens are distinct, and the 

 embryo straight. The leaves are often bipinnate. 



771. Subord, Mimosse (a large group to which the Acacia and the 

 Sensitive Plant belong) has a perfectly regular calyx and corolla, 

 the latter mostly valvate in sestivation and hypogynous, as well as 

 the stamens, which are sometimes definite, but often very numer- 

 ous ; and the embryo is straight. The leaves are frequently tri- 

 pinnate. 



772. Papilionacese are found in every part of the world, from 

 the tropics to the frigid zones : Caesalpinese and Mimosese are con- 

 fined to the tropical and warmer temperate regions. A full ac- 

 count of the useful plants and products of this large order would 

 require a separate volume. Many, such as Clover, Lucerne (Med- 

 icago sativa), &c., are extensively cultivated for fodder ; Peas and 

 Beans, for pulse. The roots of the Licorice (Glycirrhiza glabra of 

 Southern Europe) abound in a sweet mucilaginous juice, from 

 which the pectoral extract of this name is prepared. The sweet 

 pulp of the pods of Ceratonia Siliqua (Carob-tree of the South of 

 Europe, &c.), of the Honey-Locust (Gleditschia), &c., is likewise 

 eaten. The laxative pulp of Cathartocarpus Fistula, and of the 

 Tamarind, is well known ; the latter is acidulated with malic, and 

 a little tartaric and citric acid. A peculiar volatile principle 

 (called Coumarin) gives its vanilla-like fragrance to the well-known 

 Tonka-bean, and to the Melilotus, or Sweet Clover. The flowers 

 and seeds of the latter and of Trigonella cserulea give the peculiar 

 odor to Scheipzeiger cheese. Astringents and tonics are also 

 yielded by this order : such as the African Pterocarpus erinaceus, 

 the hardened red juice of which is Gum Kino ; that of P. Draco, of 

 Carthagena, &c., is Dragon's Blood. The bark of most Acacias 

 and Mimosas contains a very large quantity of tannin, and is like- 

 ly to prove of great importance in tanning. The valuable astrin- 

 gent called Catechu is obtained by boiling and evaporating the 

 heart-wood of the Indian Acacia Catechu. Leguminosse yield 

 the most important coloring matters ; such as the Brazil-wood, the 



