38 NATURE'S TEACHINGS. 



It clambers about hedges, is exposed to the fiercest winds, naa 

 large and broad leaves, and yet such a thing as a Bryony being 

 blown off a hedge is scarcely, if ever, seen. I never saw an 

 example myself, though I have had long experience in hedges. 



ANOTHER excellent example of this principle is found in the 

 Vallisneria plant, which of late years has become tolerably 

 familiar to us through the means of fresh- water aquaria, 

 though it is not indigenous to this country. 



In this plant the elastic power of the spiral cable is beauti- 

 fully developed. It is an aquatic plant, mostly found in run- 

 ning waters, and has a most singular mode of development. 

 It is dioecious i.e. the male, or stamen-bearing, and the 

 female, or pistil-bearing flowers, grow upon separate plants. 



It has to deposit its seeds in the bed of the stream, and yet it 

 is necessary that both sets of flowers should be exposed to the air 

 and sun before they become able to perform their several duties. 

 Add to this the fact that the male flower is quite as small in pro- 

 portion to the female as is the case with the lac and scale insects, 

 and the problem of their reaching each other becomes apparently 

 intricate, though it is solved in a beautifully simple manner. 



Fertilisation cannot be conducted by means of insects, as is 

 the case with so many dioecious terrestrial plants, and it is 

 absolutely necessary that actual contact should take place 

 between them. This difficult process is effected as follows : 



The female flowers are attached to a very long spiral and 

 closely coiled footstalk, and, when they are sufficiently 

 developed, the footstalk elongates itself until the flower rests 

 on the surface of the water, where it is safely anchored by its 

 spiral cable, the coils yielding to the wavelets, and keeping the 

 flower in its place. 



Meanwhile the tiny male flowers are being developed at the 

 bottom of the river, and are attached to very short footstalks. 

 When they are quite ripe they disengage themselves from their 

 footstalks, and rise to the surface of the river. Being carried 

 along by the stream, they are sure to come in contact with the 

 anchored female flowers. This having been done, and the 

 seeds beginning to be developed, the spiral footstalk again coils* 

 itself tightly, and brings the seeds close to the bed of the 

 stream, where they can take root. 



