nymph^:ace^ 69 



NYMPH^ACE^. (Water-Lilies) 



Perennial, herbaceous, aquatic plants. The very 

 numerous parts of the flower are arranged in a close 

 continuous spiral ; sepals passing gradually into petals, 

 and these into stamens. The sepals and petals are on a 

 lieshy disk, which surrounds the many -chambered, many 

 ovuled ovary, and is crowned by the sessile, radiate 

 stigmas. The embryo is very small. In our two 

 British species the carpels develop air-cells, which 

 enable the seeds to float on the surface of the water, 

 and thus ensure their dispersal. The flowers are 

 effectively protected against creeping insects by their 

 aquatic habit. They are large, white, or yellow and more 

 or less scented, yet they are not much visited by insects, 

 principally by flies and a few beetles. The seeds, which 

 are nutritious, and eaten by some birds, are embedded 

 in a slimy mass, so that some of them can hardly fail to 

 adhere to the feathers, and thus be carried from one 

 lake to another. They are crustaceous, deeply cordate, 

 glabrous, shining, and pale yellowish grey. In germina- 

 tion the cotyledons remain in the seed. 



In Nymphsea the petals are large, without a nectary, 

 and the stamens are inserted on the surface of the ovary. 

 In Nuphar the petals are small, with a nectary, and the 

 stamens are inserted below the ovary. 



Nymphsea alba (White Water-lily). — The floating 

 leaves are 5-10 inches across. In the leaves of most 

 plants transpiration takes place mainly from the under 

 side, where the majority of the stomata are situated. The 

 under side of the floating leaves of water-plants have, how- 

 ever, lost this power, and have no stomata, transpiration 

 being confined to the upper face. It is interesting that 

 some species of Nelumbium, which raise their leaves 

 above the surface, have incomplete stomata on the under 

 side, as if they were making an effort to recover the 

 structure which their ancestors had lost.^ The upper 



^ Areschoug, ' ' Der Einfluss des Klimas auf die innere Organisation der 

 Pflanzen," in Eiigler's Bot. Jahrb. ii. (1881-82). 



