102 FLASHLIGHTS ON NATURE 



vided with bright -coloured petals as advertise- 

 ments to let the insects know where honey may 

 be expected ; they secrete the sweet liquid itself 

 in order to induce their winged allies to become 

 common carriers of pollen for the benefit of the 

 begonia ; and as soon as each flower has served 

 its purpose in this respect, it drops off or is 

 retained by the plant according as it is or is not 

 wanted in future for its seed-producing properties. 

 The difference between the brother and sister 

 flowers is even more visible in the bud than in the 

 fully opened blossom. No. 3 shows us this very 

 well in the case of an unopened male blossom. 

 Here the two large petals, afterwards used as 

 platforms for the insect to alight upon, enclose 

 the smaller pair of interior ones, as well as the 

 bunch of yellow stamens. But as these stamens 

 are full of nutriment, and therefore liable to be 

 prematurely attacked by useless gnawing insects, 

 the petal above them is thickened in this part, and 

 in one of the species most cultivated in our green- 

 houses, but not figured here, is provided with little 

 protective hairs, which baffle and keep at bay all 

 hungry aggressors. I may add that the projecting 

 wings on the seed-vessel, well seen in No. i, and 

 also in the .section in No. 2, serve a somewhat 

 similar purpose : they are intended to prevent 

 hostile insects from laying their eggs at the most 

 vulnerable points in the capsule, where the grubs 

 would destroy the seeds within. The thickenings 

 above and below, also to be observed in the lower 

 figure of No. i, perform a like service. They 



