230 FLOWERS OF AQUATICS [ch. 



in whorls, even when their terrestrial relatives have a different 

 arrangement. He states that Jussiaea amazonica has the narrow 

 submersed leaves so closely whorled as to resemble the Mare's- 

 tail of our ponds, while the emersed leaves are solitary. 



Those water plants whose inflorescences rise into the air, 

 depend for cross-pollination upon insects or the wind. Those 

 which are entomophilous differ little from land plants in their 

 methods of attraction, except that, speaking very generally, a 

 blue colour perhaps occurs more rarely than in terrestrial plants, 

 while white or yellow are common^. The frequency of white 

 flowers among aquatics was noted long ago by Nehemiah Grew, 

 who, in his little book. An Idea of a Phytological History Pro- 

 pounded^ published in 1673, wrote, " to Water-plants more 

 usually a White Flower." The rarity of blue flowers among 

 hydrophytes may be accidental, but those who take a teleologi- 

 cal view of these matters prefer to attribute it to the fact that 

 blue does not contrast vividly with the colour of a water surface 

 with its sky reflections. It is possible that some water plants, 

 such as Lemna^y are pollinated by crawling insects, although 

 they possess no special means of attraction. 



A certain number of aquatics appear to have given up insect 

 pollination and taken to anemophily, often with concomitant 

 simplification of the flower, e.g. Hippuris (Fig. 151) and Myrio- 

 phyllum (Fig. 144, p. 221). This change of habit may be 

 associated with the fact that the number of insects flying over a 

 water surface is probably less, on an average, than the number 

 over a corresponding land surface. Peplis Portula (Fig. 152, 

 p. 232) seems to be actually in a state of transition from 

 entomophily to anemophily. There are six fugacious little white 

 petals, and a small amount of honey is secreted^. But the 

 flowers are very inconspicuous, and no insect visitors appear 

 to be attracted. The stigma becomes ripe a little sooner than 

 the stamens, but they bend inwards over it and pollinate it*. 



Myriophyllum is an example of a wind-pollinated genus, in 



1 Schenck, H. (1885). 2 See p. 80. ^ MacLeod, J. (1894). 



4 Willis, J. C. and Burkill, I. H. (1895). 



