208 EVOLUTION OF PLANTS 



ria, etc., in the character of the flowers. The parts of 

 the flower are all separate, and in the lower members of 

 the group, of indefinite number. This is well- shown 

 in the various species of buttercups (Ranunculus). The 

 Ranunculus family also offers some interesting examples 

 of specialization within a group which nevertheless 

 retains a very primitive type in the arrangement of the 

 floral parts. In Anemone (Fig. 55, A) and in Clematis, 

 as well as other genera, the petals are quite suppressed 

 or inconspicuous, while their place is taken by the large 

 petaloid sepals. Some other genera, like the columbines 

 (Aquilegia), larkspurs (Delphinium), and monkshood 

 (Aconitum), have the parts of the flower extraor- 

 dinarily modified in form, and yet retain the primitive 

 completely separated carpels and numerous stamens 

 (Fig. 50, B, C). These modifications of the flower are 

 all intimately connected with insect-pollination, and 

 many of the more specialized forms like Delphinium 

 and Aquilegia are probably entirely dependent upon 

 insects or humming-birds for pollination. On the other 

 hand, some species of Ranunculus with inconspicuous 

 flowers are always self-fertilized. Other Polycarpicae 

 are the water-lilies (Nymphseacese, Fig. 50, E), magno- 

 lias, and several other less familiar families. 



Another probably primitive group of the Choripetalse 

 is the order known as the Centrospermee. The lowest 

 members of the series, the buckwheat family (Poly- 

 gonacese, Fig. 49, E), the pig-weeds (Chenopodiacese), 

 etc., have flowers which recall the peppers and some of 

 the simple Monocotyledons in having the single ovule 

 formed directly from the apex of the floral axis (Fig. 

 49, F, o). The higher ones have numerous ovules, 



