472 



DICOTTLEDONES. 



are very small or are entirely wanting ; stamens monadelplions. 

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

 often terminate in a thorn. The strongly-winged stems in G. sagittalis 

 are its most important organs of assimilation. Bossiwa rufa has flat branches, 

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

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

 simple and ternate leaves on the same shoot ; style spirally rolled. 

 Cytisiis (Laburnum). Ulex (Furze ; in U. europaus, the seedlings bear 

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

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

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

 adnate stipules. Eetama. 



9. HEDYSARE^; are especially recognised by having the ovary 

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



the fruit thus becomes a lomentum, dehiscing 

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

 Ornithopus(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 liypogcea (Earth-nut) 

 has a pod which is abstracted between the 

 seeds, and is indehisceut, but is not multi- 

 locular nor a true lomeutum ; 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. Lcsmodiiim gyruns is well- 

 known for its motile leaflets. 



10. DALBERGIE.E. 25 genera ; especially in Tropical America ; the majority 

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

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

 (MaclfCErium, Dalbergia, Centrolobium, etc.), in others, again, a drupe, e.g. in 

 Dipteryx (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 gyuceceuin 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. Hediisamm 

 corcnarium. 



