CONCLUSION 179 



advances it becomes more and more complex, and when 

 we reach still higher plants further surrounding tissues 

 are pressed into its service and it becomes enclosed in 

 the carpel of the highest flowering plants. After that the 

 seed itself has fewer general duties, and instead of those 

 of the Gymnosperms with large endosperms collecting 

 food before the embryo appears, small ovules suffice, 

 which only develop after fertilization is assured. The 

 various families of flowering plants have gone further, and 

 the whole complex series of bracts and fertile parts which 

 make up a flower is adapted to ensure the crossing of 

 male and female of different individuals. The complex 

 mechanisms which seem adapted for " cross fertilization " 

 are innumerable, and are found in the highest groups of 

 the flowering plants. But some have gone beyond the 

 stage when the individual flowers had each its device, 

 and accomplished its seed-bearing independently of the 

 other flowers on the same branch. These have a com- 

 bination of many flowers crowded together into one 

 community, in which there is specialization of different 

 flowers for different duties. In such a composite flower, 

 the Daisy for example, some are large petalled and 

 brightly coloured to attract the pollen -carrying insects, 

 some bear the male organs only, and others the female 

 or seed-producing. Here, then, in the most advanced 

 type of flowering plant we get back again to the sepa- 

 ration of the sexes in separate flowers; but these flowers 

 are combined in an organized community much more 

 complex than the cones of the Gymnosperms, for ex- 

 ample, where the sexes are separate on a lower plane of 

 development. 



It seems possible that an important group, if not the 

 dominant group, of flowering plants in the future will be 

 so organized that the individual flowers are very simple, 

 with fewer parts than those of to-day, but that they will 

 be combined in communities of highly specialized indi- 

 viduals in each flower head or cluster. 



As well as this, in other species the minute structure 



