POLLINATING AGENTS ity 



Surface, Which is exposed to the view of insects as 

 they fly about in quest of food. When the petals are 

 modified, or not fully developed, or absent, the sepals 

 often take over the function that properly belongs 

 to the petals, as in Holmskioldia ^anguiHea atid Ster^ 

 culia Roxburghii (ushli) (see Plate V, b), — trfeefe 

 with a deep-red calyx. The petals dre frequently 

 helped by the sepals in the work of allurement, so 

 that both the perianth whorls minister to the same 

 end. It frequently happens that flowers which are by 

 themselves inconspicuous are rendered conspicuous 

 by coloured bracts, as in bagan-bilas {Boiigainvillea), 

 lalpata {Euphorbia pulcherrima), and Houttuynia 

 reflexa. In Musscenda one of the sepals develops 

 into a large white-coloured leaf. Small inconspicuous 

 flowers are often made conspicuous by their associa- 

 tion in an inflorescence. Thus the capitula of the 

 CompositcB are visible from a great distance, so that 

 they receive more insect visits than other plants. The 

 ray florets are often ligulate, by which the end in view 

 is attained more successfully. The enlargement of 

 the marginal flowers of an inflorescence is often met 

 with, as in the corymbs of many Cruciferce and in the 

 umbels of many Umbelliferce. Similarly, the inner 

 flowers of an inflorescence are often sexual and the 

 outer ones asexual, the latter greatly developing their 

 attractive parts at the expense of the stamens and 

 pistil, as in many Compositce, Umbelliferce, and Cruci- 

 ferce ; or the upper flowers may serve to attract while 

 the lower flowers are concerned with reproduction. 

 Occasionally the perianth leaves are dull-coloured 

 and unattractive, and to compensate for this the 

 stamens are modified into bright-coloured petaloid 

 staminodia, as in most Scitaminacece ', or the anthers 

 are brightly coloured, as in Mignonette. Conspicu- 



