POLYCARPICJE. 



387 



projecting thorny ribs on the lower surface. In the intercellular 

 passages of the leaves are some peculiar, stellate cells. 



Nuphar has 5 sepals, and an hypogynous flower. The petals, which 

 are small, have a nectary on the back ; the coloured inner side of the sepals 

 functions as petals ; the ovate gynoeceum is quite free. N. luteum is a native 

 plant (Yellow Water-Lily), with, most frequently, 13 petals and 10-16 loculi in 

 the ovary. The rhizome is horizontal, as much as 5-6 cm. in thickness, and 

 bears on its under surface a number of roots, which on dying-off leave deep 

 scars ; the leaves are borne in spiral lines, and the flowers are solitary in 

 certain leaf-axils. The construction of the rhizome is very peculiar ; the 

 vascular bundles are scattered and closed as in a monocotyledonous stem. 



A EC 



Fio. 333. Nymphcea; A flower in longitudinal section, the most external leaves being 

 removed; I? fruit; C seed of Nnphar (longitudinal section); the perisperin at the base, 

 the endosperm at the top surrounding the embryo. 



Nymplisea has 4 sepals, and the flower is more or less <'pi<jy- 

 nous. Petals and stamens are inserted at different heights on the 

 ovary to just beneath the stigma (Fig. 383). NympJisea alba (White 

 Water-Lily). Victoria regia from the Amazon, and Euryale ferox 

 from Asia, have entirely epigynous flowers. The shield-like leaves of 

 Victoria are as much as 2 metres in diameter, and the edge is bent up to a 

 height of 5-14 cm. ; the flowers are 20-40 cm. in diameter, and change in 

 twenty-four hours from white to rose-red. A development of heat, as much as 

 14C. above the temperature of the air, together with a strong formation of 

 car'onic acid, has been observed during flowering. 



POLLINATION. Ntjmphaa alba and other species of the sub-genus Symphy- 

 topleura are self-pollinated ; the sub-genus Leptopleura is insect-pollinated. 

 Nuphar and Victoria can effect self-fertilisation ; Euryale is self-fertilised, often 

 in entirely closed and submerged flowers. The dissemination of the seeds in 

 Nuphar luteum is effected by the fruit, which rests on the water, becoming de- 



