34 TROPICAL AGRICULTURE chap. 



by similar glands or cushions on the petals or the stamens 



themselves. On examination, these organs may be seen as 



a small swelling or as special receptacles or spurs, from 



which the nectar exudes. All the various glands, cushions 



and receptacles exuding sweet juices, as mentioned above, 



are generally called nectaries. 



Birds and ^^'^ h3.ye seen how insects and birds go to flowers to rob 



irs-^'^the^"''' ^^^ nectar, but nature has wisely provided that they shall, 



flo%yers, at the samc time, render a service to the plant by assisting 



whilst they . . . ...,.._, . 



feed on the ^1 the important process of fertilisation. Flowers are of an 



nectar. infinite variety of form ; but, no matter how the several 



parts are arranged, insects cannot get at the nectar without 



coming in contact with the anthers, so that the pollen 



escapes and clings to them. And thus, when another flower 



is visited, the pollen is brushed against the sticky stigma 



and so remains to effect its important work. This is the 



commonest way in which flowers are fertilised by insects, 



but in other instances the arrangement of the flower to 



A wonderful cffcct pollination is simply marvellous. Aristolochia trilobaia 



theafrangl- ^^ a curious climbing plant that grows wild in Jamaica, 



menis of Dominica, and other islands of the West Indies. Its 



Nature to ' 



ensure ferti- flowcr is vcry pretty ; there is no corolla, but the coloured 

 inTea^ ^ calyx is formed like a pitcher with a curved swan neck. 

 This neck has a lid-like covering prolonged into a tail which 

 freely waves in the wind and thus serves to arrest the atten- 

 tion of insects. The lid prevents rain entering the pitcher, 

 but it allows free access to flies and other small animals. 

 The inner side of the neck forms a tube leading down to 

 the inflated bottom of the flower ; and it is set with hairs 

 all sloping away from the entrance, and with their points 

 directed towards the interior ; so that, although they ofl'er 

 no obstacle to an insect entering the cavity of the flower, 

 they effectually prevent its exit. A fly, then, entering the 

 pitcher in search of nectar, is kept imprisoned until it has, 

 by its movements, caused the pollen to be applied to the 

 stigma ; and when this occurs, the hairs gradually collapse^ 



