THE VICTORIAN NATURALIST, 129 



insects to visit flowers, and what advantage accrues to a plant 

 from the visits with which its flowers are favoured ? The answer 

 is, that the inducement is in some cases care of young, in others 

 the desirabihty of securing themselves against dangers from 

 storms, and most commonly of all it is the craving for food. 

 Flowers, however, do not provide animals with breeding-places, 

 with temporary shelter or suitable nutriment without claiming a 

 reciprocal service^ but have their parts so adjusted that their 

 visitors become laden with pollen, which is then transported to 

 other flowers and deposited on their stigmas, where it initiates a 

 series of changer, resulting in the setting of the seed. 



The efficacy of all the arrangements for promoting the quick 

 and easy obtaining of food from flowers by bidden guests is 

 obviously much enhanced by the existence of others for the 

 exclusion of hurtful and undesired visitants. As hurtful may be 

 characterized all such animals whose visits interfere with or pre- 

 vent the speedy transfer of the pollen from flower to flower. 

 Such are small wingless animals, which must of necessity reach 

 the honey and pollen on foot. Su|)pose such a little pedestrian 

 has reached a flower and covered itself with pollen ; it has now, in 

 order to transfer this pollen to a stigma on another plant, a long 

 and toilsome journey, beset with dangers to the pollen, quite 

 apart from the length of time taken. Shortly, the pollen may be 

 easily rubbed off" on the journey, or it may be washed off by the 

 rain. How otherwise it is with the lightly-flying insects. They 

 dart from plant to plant with extraordinary rapidity and visit 

 half a dozen flowers within a minute or so, thus transferring the 

 pollen new and fresh. Winged insects are therefore in the most 

 cases ideal agents for the crossing of flowers, and are the most 

 welcomed of all guests. 



The simplest case, where insects after reaching the flowers are 

 covered with the pollen, is that where the insects rove and climb 

 about the flowers and so get powdered all over with pollen. This 

 hai pens in inummerable plants which, owing to the association 

 of large numbers of flowers in umbels, fascicles, spikes, and 

 capitula, afford a playground, richly furnished with slender waving 

 stamens, where pollen is easily to be shaken or brushed off the 

 anthers on every liand, although each single blossom only con- 

 tains a few stamens. 



Remarkable is the fact that insects after being imprisoned for 

 a lime in the flower of Aristolochia clematitis are quite covered 

 with pollen when they emerge. The way into the enlarged base 

 of the flower is over a convenient ligulate alighting place and 

 through a dark and comparatively narrow passage lined with 

 hairs. The free extremities of these hairs point inward, and 

 permit visitors from the insect world, small black midges, to pass 

 into the chamber. Not uncommonly 6 to lo such flies may be 



