472 



DICOTYLEDON ES. 



are very small or are entirely wanting; stamens monadelphous. 

 Genista (Dyer's-weed) has apparently simple leaves ; the branches 

 often terminal e in a thorn. The strongly-winged stems in G. tagittal'u 

 are its most important organs of assimilation. Bosnaxi rnfa has flat branches, 

 its leaves being reduced to small, pointed stipules. Sarotkamnits (Broom) 

 has switch-like, angular branches and often both the apparently 

 simple and ternat v e leaves on the same shoot ; style spirally rolled. 

 Cytisus (Laburnum). JJlex (Furze; in U. europecus, the seedlings bear 

 a few foliage leaves, but the leaves succeeding these are modified into thorns) ; 

 Spartium; Crotalaria,etc. Lupinus (Lupin) is allied to this group; 

 it has a thick, often somewhat fleshy pod, and digitate leaves with 

 adnate stipules. Retama. 



g. HEDTSAEEJE are especially recognised by having the ovary 

 divided by transverse septa into as many cells as there are seeds, 

 the frnit thus becomes a lomentum, dehiscing 

 transversely into nut-like joints (Fig. 513). 

 Orm'/topM.s(Bird's-foot); Coronilla; Hippocrepis; 

 Onobrychis (Sainfoin) has a fruit with only 1 

 joint (i.e. a 1-seeded nut) ; Desmodium; Alhayi ; 

 Hedysarum, etc. Arachis hypogcea (Earth-nut) 

 has a pod which is abstricted between the 

 seeds, and is indehiscent, but is not multi- 

 locular nor a true lomentum ; it is reticulately 

 wrinkled externally, and ripens underground ; 

 the basal part of the ovary is prolonged after 

 flowering, attaining a length of several inches, 

 and buries the young fruit in the soil. The 

 embryo is straight. Desmodium gyrans is well- 

 known for its motile leaflets. 

 10. DALBERGIEJE. 25 genera ; especially in Tropical America ; the majority 

 are trees, a few shrubs or lianes ; the leaves are simple or imparipinnate. The 

 fruit is indehiscent in all; in some it is a winged, in others a wingless nut 

 (BJachan-hnu, Dalbergia, Centrolobium, etc.), in others, again, a drupe, e.g. in 

 Diptenjx (Tonquin-bean) and Andira. In some genera the embryo is straight. 



POLLINATION. Especially effected by Bees. The nectar is secreted by a 

 ring or disc-like portion round the base of the gynoeceum or the inner surface 

 of the receptacle. The flower is constructed with a peculiar mechanism to 

 ensure cross-pollination by insects. The pollen is shed just before the flower 

 opens, and is retained in a pouch formed by the keel. An insect visiting the 

 flower uses the wings and keel for a landing-stage, and in attempting to reach 

 the honey presses down the wings and the keel which are locked together near 

 the standard; the st>lar-brush by this means is forced through the apical 

 opening of the keel and a little pollen is thus swept out and deposited upon 

 the abdomen of the visiting insect as it presses against the apex of the keel ; 



FIG. 513. Hedysarum 

 coronarium. 



