572 



BOTANY 



PART II 



B. DiALYPETALAE 



Flowers with a green calyx and a coloured corolla. 



Order 1 1 . Polyearpicae 



This large order includes a number of families of very different 

 general appearance but exhibiting as common characters a superior 

 gynaeceum with the carpels free from one another, and a spiral 



Fig. 553. — Nympliaea albn (J nat. size). Tlie spiral arrangement of the stamens and petals 

 is shown by their insertions on the ovary to the left. 



arrangement of the members of the flower. The tendency to con- 

 siderable increase in the number of stamens stands in relation 

 to this. 



It is, liowever, to be noted that by no means all the plants of the families united 

 in this order exhibit the above characters in the same degree. The characteristic 

 features may indeed Ijc completely wanting, tliongh the existence of intermediate 

 forms leaves no doubt that the genera in question must be classed here. 



Family 1. Nymphaeaceae (^'). — Aquatic plants with submerged or floating 

 leaves, the latter often of very large size ; when Ijoth types of leaf are present 



