HERBACEOUS AND WOODY DICOTYLEDONS 397 



CALTI1A (MARSH MARIGOLD) AND RANUNCULUS (BUTTERCUP) 



Habitat and habit. Caltha palustris, the marsh marigold, differs 

 from the majority of the buttercups in being a hydrophyte, 

 inhabiting marshes and swamps along the margins of streams 

 and lakes. The heart-shaped, rounded leaves are mostly radi- 

 cal, or root, leaves (Fig. 248), but some leaves also are found 

 on the flowering 

 stems, which grow 

 up annually and 

 produce clusters 

 of bright yellow 

 flowers. The but- 

 tercups are quite 

 diversified in both 

 habitat and habit, 

 being represented 

 by true mesophytes 

 and hydrophytes 

 as well as by cau- 

 lescent and acau- 

 lescent species. 



Reproduction. In 



FIG. 248. Habit and reproductive organs of the marsh 

 marigold (Caltha palustris) 



a, the plant; 6, stamen; c, long section of a pistil, showing 

 the ovules on the placenta ; d, ovule ; e, floral diagram 



both Caltha and 

 the true butter- 

 cups the flowers 

 are simple and 

 regular, and are thus representative of the simplest types of 

 floral structure among the plants of the Ranunculus family. 

 The account already given of the flower of Caltha indicates its 

 close alliance with the spiral, hypogynous flowers whose struc- 

 ture is similar to that of a strobilus (Fig. 200). 



Cross-pollination is provided for in both Caltha and the butter- 

 cups, although close-pollination and self-pollination are possible 

 in most cases. The following account of the adaptation of the 

 flowers to pollination is applicable to both Caltha and the 

 common buttercups. 



