Ill 



] 



NELUMBO AND LI MN ANTHEM UM 



39 



almost complete absence, both in leaf and stem, of these fea- 

 tures that may be regarded as primitive for the family. Nelumbo 

 may possibly be interpreted as the most highly differentiated 

 of the Waterlilies, and part of its peculiarities may perhaps 

 be due to the fact that it is rather a marsh plant than a true 

 aquatic. Possibly it is a genus descended from aquatic ancestors, 

 which has reverted in some degree towards a terrestrial life^. 

 Another genus which, though extremely distant from the 

 Waterlilies in its systematic position, yet in its life-history 

 resembles them in some degree, may be mentioned at this 



Fig. 21. Sketch map showing the existing and geologic distribution of Nelumbo. 



The obliquely lined areas represent the range of the two existing species, while 



the Cretaceous and Tertiary records which occur outside these areas are marked 



by solid black circles. [Berry, E. W. (1917).] 



point. This is Limnanthemum {Villarsia\ a member of the 

 Gentianaceae, which is represented in Britain by the beautiful 

 L. nymphoides with its fringed yellow flowers. Like Castalia and 

 Nymphaea it has a rhizome at the bottom of the water while its 

 leaves float at the surface (Fig. 22, p. 4 1). The length of the inter- 

 nodes of the rhizome varies with the time of year^ (Fig. 23, 

 p. 41). In the autumn, the leaves are closely packed and the 

 adventitious roots hold the axis with its abbreviated internodes 

 close to the ground. In the spring, elongated internodes are 

 1 Dollo, L. (19 1 2). 2 Wagner, R. (1895). 



