INSECTS AND FLOWERS 221 



Darwin showed long ago that this plant is sterile when 

 protected from the visits of these insects. The small 

 flowers of the ivy and red-currant have each a kind of 

 central cushion whereon the nectar glistens in profusion. 

 Apparently it is free to be sipped by all and sundry. Yet 

 in point of fact it is only accessible to " short-tongued 1 ' 

 insects — those with long suctorial mouth-parts, such as 

 butterflies, moths, and humble-bees, being in much the 

 same case as the fabled stork to whom the fox offered 

 food in a shallow dish. Many flowers, however, cater 

 exclusively for " long-tongued " insects. This is the case 

 with the honeysuckle {Lonicera periclymenum). The 

 inflorescence consists of a number of closely crowded 

 blooms, each of which has a long tubular portion, at the 

 far end of which nectar is secreted. The five stamens and 

 the pistil project from the mouth of the tube. The newly 

 opened flower is almost white, while the style of the pistil 

 bends downwards ; but the stamens stand out stiffly. In 

 its later stage the flower becomes yellow, its exhausted 

 stamens bend down, while the style of the pistil rises up 

 and lengthens, so that the stigma is brought into the 

 position originally occupied by the anthers. The flowers 

 exhale a strong scent, especially in the evening, and are 

 visited chiefly by hawk-moths. When a moth hovers in 

 front of a flower in the first stage, it is unlikely to touch 

 the stigma, but is almost certain to get dusted with pollen 

 as it thrusts its proboscis into the tube to get at the 

 nectar. If it then proceeds to a flower in the second 

 stage, the stigma will come into contact with the region 

 of the insect's body on which the pollen was deposited. 

 Humble-bees also visit honeysuckle, but they effect cross- 

 pollination less neatly than the hawk-moths. 



The Indian Nasturtium {Tropceolum) has the calyx 

 produced into a long tubular spur, which holds the nectar. 



