954 



THE NATURE BOOK 



large piece of meat. As well, the flowers 

 of the Aristolochia emit a horrible odour, 

 which is so nauseating that a person 

 cannot stay long in the vicinity of a 

 blossom. That this simulation is not in 

 vain, may be gathered from an examina- 

 tion of the interior of the bloom, which 

 is crowded with flies come in search of 

 the imagined dainties. 



Having attracted the insect to the 

 flower, it is necessary to make sure that 

 it does not go away without its burden 

 of pollen. In almost every case of a 

 flower fertilised by insect agency, the 

 pollen grains are either sticky or else 

 covered with excrescences which cause 

 them to adhere readily to any object. 

 As a curious contrast, the pollen pro- 

 duced by wind-fertilised plants is almost 

 always smooth and free from any pro- 

 jections. With a large number of flowers, 

 especially in the case of the Compositae, 

 the insect visitor in his wanderings brushes 

 up against the anthers of the stamens, 

 and in this way becomes dusted with 

 the pollen, which is likely to be carried 

 to the next bloom visited. The Peacock 

 Butterfly, which sips nectar from the 

 clustered bloom of the Scabious, cannot 

 fail to get a certain amount of pollen 

 over his legs and body. In like manner 

 the bee which blunders into the Crocus 

 blossoms will, both at her entry and exit, 

 be certain to have her body freely 

 powdered with the golden dust. 



In such cases as these we see the 

 relations of the plant and its insect helper 

 at their simplest. Far more elaborate 

 arrangements have been devised to 

 ensure the effective distribution of pollen 

 by insect agency. Many of these are 

 especially remarkable owing to the fact 

 that the flower is designed for the visits 

 of one class of insect, or perhaps for a 

 single species. Thus a number of exotic 

 plants which are introduced into British 

 gardens can never be effectively cross- 

 fertilised, simply because none of our 

 indigenous insects is fitted for the task. 

 A ratlier curious case is that of a Brazilian 

 species, Araujia albens, a plant which is 

 of fairly easy culture in the south of 

 England. In its native country the 

 cross-pollination of the Araujia is carried 

 out by large humble-bees, strong enough 

 to force their way in and out of the 



curious trap-like contrivance which 

 guards the pollen masses. In other 

 places, however, where the plant has 

 been introduced, the flowers are largely 

 visited by moths, which, unaware of the 

 curious device, thrust in their probosces 

 in search of the nectar. Too late the 

 unfortunate insects find that they are 

 caught in a trap from which they have 

 not sufficient ingenuity to release them- 

 selves. So they flutter away their lives 

 in vain endeavours to escape. 



Undoubtedly the largest number of 

 special arrangements in flowers have 

 been made with a view to the reception 

 of bees. However these extraordinary 

 relations have arisen, the plant could 

 scarcely have secured a more industrious 

 and systematic worker. It has been 

 computed that an average bee will visit 

 three or four hundred blossoms on a 

 summer day, so that even where flowers 

 are in great profusion we may take it 

 that not one will escape attention from 

 the winged visitors. The way in which 

 many flowers have been specially designed 

 in order to keep out unwanted callers has 

 been dealt with elsewhere, but it is 

 interesting to consider the ease with 

 which the right visitor can obtain an 

 entrance. Most people must have 

 watched a humble-bee open that " strong 

 box," the Antirrhinum flower. How con- 

 venient is the little platform on which the 

 insect may alight and secure a firm hold 

 with her legs in order that the contrivance 

 may be forced open ! 



Even as the bee takes her measure 

 of the nectar, she receives a dusting of 

 pollen from the anthers. More ingenious 

 still is the arrangement in the case of 

 the Pea. In this flower the stamens 

 and pistil are contained in a process 

 formed by two petals joined together, 

 generally spoken of as the keel. At a 

 certain stage in the development of the 

 blossom, the anthers discharge their 

 sticky pollen into the cavity at the tip 

 of the keel. Now it is just at this time 

 that the Pea makes its greatest effort to 

 attract attention ; the standard is fully 

 spread, the fragrance given out is at 

 its strongest, whilst the supply of nectar 

 is all in readiness for the expected visitor. 

 At last the bee alights, taking up its 

 position on the two lateral petals while 



