DICOTYLEDONS 



207 



are reduced forms, but this cannot be taken for granted, 

 and further investigation is needed before definite con- 

 clusions can be reached as to their systematic position. 



The Amentacese are largely inhabitants of the cooler 

 parts of the world, some of them, like the willows and 



-DC 



FIG. 50 (Polycarpicse j . A, section of the flower of a buttercup (Ranun- 

 culus) ; the numerous carpels are entirely separate ; B, flower of wild 

 columbine (Aquilegia) ; the petals, p, are modified into tubular necta- 

 ries ; C, flower of a larkspur (Delphinium) ; the flower is strongly 

 zygomorphic, and the two upper sepals form the spur, or nectary ; D, 

 flower of the tulip-tre'e (Liriodendron), one of the Magnolia family; 

 the flower is divided lengthwise to show the numerous stamens, and 

 the separate carpels grouped together upon the elongated central recep- 

 tacle; E, flower of the wild lotus (Nelumbo), one of the water-lily 

 family ; F, young fruit of the lotus, consisting of the enlarged conical 

 receptacle, with the separate carpels, car, embedded in cavities in its 

 upper surface. 



birches, being among the most northerly of all trees and 

 shrubs. 



A second primitive group of Choripetalse is the 

 Polycarpicse represented by the buttercup family and 

 its allies. Some of these also recall one group of the 

 Monocotyledons, the Apocarpae, e.g. Alisma, Sagitta- 



