534 



BOTANY OF THE LIVING PLANT 



If a large insect, perching on the lower lip of the flower of Sage, inserts its 

 proboscis, the sterile lobes will be pressed upwards, and this will cause the 

 fertile lobes to descend, depositing the pollen over a definite area of the insect's 

 back. In older flowers that have already shed their pollen, the style elongates : 



FIG. 439. 



Pollination of Salvia pratensis. i, Flower visited by Humble Bee, showing the 

 projection of the curved connective from the helmet -shaped upper lip, and the deposit 

 of the pollen on the back of the Bee. 2, older flower, with connective withdrawn 

 and elongated style. 4, the staminal apparatus at rest, with connective enclosed 

 within the upper lip. 3, the same when disturbed by the entrance of the proboscis 

 of the Bee in the direction of the arrow. / = filament. c = connective. s=-thc 

 obstructing half of the anther, which produces no pollen. (After Strasburger.) 



its lobes diverge and take such a position that the stigma touches that region 

 of the insect's body which received the pollen from the younger flowers. 

 Cross-pollination thus follows on repeated visits to flowers of various ages ; 

 and it is effected with a high degree of certainty, though in each flower only 

 two half-anthers are fertile. Economy of pollen follows on perfection of the 

 mechanism. 



ORDER: SYNANDRAE. 



Family: COMPOSITAE. Examples; OX-EYE, DANDELION, CENTAURY. 



The Family of the Compositae consists mostly of herbs. It is of world- 

 wide distribution, and is the largest Family of Flowering Plants. It is char- 

 acterised by having the gamopetalous flowers collected into capitula, or heads. 

 Each head is surrounded by a common involucre of protective bracts. The 



FIG. 440. 

 Inflorescence of Daisy : a capituluin. (After Figuier.) 



whole head is equivalent biologically to a single flower, and behaves as such, 

 though morphologically it is a closely packed, spicate inflorescence. The 

 Dandelion and Daisy are familiar examples (Fig. 440). The structure of the 



