558 



BOTANY 



PAP.T II 



toothed, never deeply lobed or incised. Simple leaves are of rare 

 occurrence in this order, and are usually small. 



Just as in most of the more natural orders, the attempt to divide the Legu- 

 minosae into families is attended with difficulty, as the extreme forms are linked 

 together by all possible intermediate stages. The 

 whole order is in consequence sometimes regarded 

 as a single family, in which the main groups 

 take the position of sub-families. In their typical 

 representatives, however, these groups are so char- 

 acteristically developed that it seems best to con- 

 sider them as distinct families. 



Family Mimosaeeae. — Flowers actino- 

 morphic ; corolla absent, or if present, with 

 petals VALVATE in the bud; andrcecium 

 haplostemonous, diplostemonous, or poly- 



STEMONOUS, USUALLY WITH FREE STAMENS ; 



embryo straight (Fig. 533). 



This family consists for the most part of shrubs, 

 lianes or small trees, with doubly pinnate leaves, 

 or, as in many Australian species, with phyllodia 

 (cf. p. 46). The flowers are small, in dense 

 heads or spikes, whose bright, usually yellow, 

 colour is due to the long stamens which project 

 beyond the inconspicuous perianth. The more 

 important genera are Acacia and Mimosa. Both 

 genera are largely represented in the Tropics. 

 Mimosa pudica, the Sensitive Plant, belongs to this 

 family ; it is sometimes cultivated in hot-houses, 

 but in its native land it is a troublesome and worth- 

 less weed. In Australia the Mimosaeeae occupy an 

 important position, and together with Eucalyptus 

 trees they form the chief part of all the woody 

 vegetation, while in the dry regions of South Africa, 

 in the form of thorny shrubs {e.g. Acacia horrida), 

 they often constitute the only woody plants. 



Officinal. — Acacia Senegal, a shrub native of 

 Fig. im.-Tamarindus indica. the Nile countries and Senegal, yields Gummi 

 Fruit in longitudinal section, arabicum. The gum, which is formed by the dis- 

 M, The fleshy mesocarp.— Offi- organ i sa ti n of the stem-parenchyma, exudes as a 

 ^ (After Berg and tMot fluid from wounds in the stemgj and after . 



wards hardens. Catechu is an extract made from 

 the heart-wood of Acacia Catechu and A. Suma (East Indian trees). 



Family Caesalpiniaeeae. — Flowers more or less zygomorphic; 

 corolla sometimes absent, when present, NOT AT ALL OR ONLY IMPER- 



FECTLY PAPILIONACEOUS, with ASCENDING IMBRICATE ESTIVATION 



(i.e. the posterior petal overlapped by the others) ; andrcecium with 

 free stamens, often reduced. Embryo straight (Figs. 534, 535). 



OlMAL. 



Schmidt.) 



