THE DICOTYLEDONES 



1629 



condition in this section has been reached by reduction from a folhcle. 

 In the second section is the genus Clematis, which is separated from the 

 other genera by the valvate aestivation of its four or more petaloid sepals. 

 The plants are generally woody climbers with opposite, simple or compound 

 leaves, sometimes with sensitive petioles which function as tendrils. The 

 stamens and carpels are numerous. The third section includes the genera 

 Myosiirus and Adonis, in which the single ovule is pendulous, and Ranun- 

 culus in which it is erect. The flowers usually have five green sepals and 

 five or more coloured petals, generally with a nectary at the base of each. 

 The stamens and carpels are numerous and spirally arranged. They are 

 mostly herbs of small size and some are annuals. Others are aquatic and 

 some, like Ranunculus repens, form runners. 



In the genus Thalictrum the plants have tripartite leaves and numerous 

 small flowers borne in panicles or corymbs. The perianth consists of four 

 or five small greenish segments which soon fall oflF leaving a mass of stamens 

 which are often brightly coloured (Fig. 1487). The fruit is either an etaerio 

 of akenes or may be reduced to a single akene. The genus is essentially 



Fig. 1488. — Geographical distribution of Tlialictniin. (After Hutchinson.) 



a north temperate one, occurring widely in the north of Europe, Asia and 

 America (Fig. 1488). 



In Ranunculus (Fig. 1489) the flowers are usually protandrous. Insects 

 are attracted to the flowers by the yellow petals. At the base of each petal 

 is a nectar pit formed by the prolongation of a membranous scale. On 

 dehiscence the anthers are inclined towards the petals thus preventing 

 pollen falling on the styles. Later the stamens fall ofT leaving the stigmas 



