THE DICOTYLEDONES 



1715 



tion, which distinguishes it from the Sarraceniaceae in which the placenta- 

 tion is parietal. 



The third and last family is the Droseraceae. There are five genera 

 with 100 species, all but three of which belong to the genus Drosera, the 

 only genus of the order represented in the British Flora (Fig. 1588). This 

 genus, which includes the Sundews, is widely distributed in temperate and 



Fig. 1588. — Drosera rotundifoUa. The commonest British 

 species with basal rosettes of glandulose leaves. 



tropical regions of the New and Old Worlds. Of the other three genera, 

 all of which are monotypic, Drosophyllum hisitanicum grows wild in Morocco, 

 Portugal and southern Spain; Dionaea miiscipida (Venus' Fly-trap) 

 (Fig. 1589) is confined to the south-eastern United States; while Aldrovanda 

 vesiculosa occurs in central and southern Europe, north and east Asia, India 

 (Bengal) and Australia (Queensland). 



The leaves in Drosophyllum, Drosera and Dionaea form a rosette on the 

 ground and are modified to entrap flies (Fig. 1590) while in Aldrovanda the 

 plant is a rootless aquatic in which the leaves are modified for the same 

 purpose. 



The flowers are hermaphrodite, actinomorphic and either pentamerous 

 or rarely tetramerous, often with an increase in the number of the stamens 

 and a reduction in the number of the carpels. 



The ovules are numerous, anatropous with parietal or basal placentation. 



This family, though obviously closely related to the others already 



