Cheeseman. — On Vallisaeria spiralis in New Zealand. 389 



whose flowers are fertilised in quite a different manner, and 

 of these Vallisneria is a typical example. In their case the 

 pollen, instead of being blown by the wind or carried by 

 insects, is conveyed to the female flower by means of rafts 

 floating on the surface of the water. Let us now see how 

 this takes place. 



The stems of Vallisneria are short, and almost concealed 

 by the mud amongst which they grow ; but here and there 

 they give off offsets or stolons. These ai'e easily detached 

 from the parent plant, and readily put down roots into the 

 mud, thus starting life on their own account. It is by their 

 means that the rapid increase of the species is insured when 

 seeds are not produced, as is the case at Lake Takapuna. 

 The leavds are in tufts at the top of the stem, and vary in 

 length according to the depth of the water, sometimes being 

 quite short, at other times reaching a length of 12ft., or even 

 loft. They are always narrow for their length, resembling 

 long ribbons, and float freely in the water with their tips 

 just below the surface. Like many water-plants, they are so 

 delicate in texture that if the water is removed they are 

 unable to support their own weight, and sink limp and 

 withered on the mud. 



The flowers are unisexual, and the two sexes are borne 

 on different plants. The male flowers are small and very 

 numerous, and are closely packed within a delicate bladder- 

 like spathe. Each little flower consists of three perianth 

 leaflets, enclosing two or three stamens. The stalk which 

 supports the flowers is short, seldom reaching more than Gin. 

 above the surface of the mud, so that the flowers come to 

 maturity far below the surface of the water. The female 

 .flower is single, and is at first enclosed within a long tubular 

 spathe. It has three broad perianth leaflets, within which 

 are three large fringed and lobed stigmas. The stalk of the 

 female flowers lengthens in an extraordinary degree as the 

 flower approaches maturity, and has been known to grow at 

 the rate of more than a foot in twenty-four hours. When it 

 reaches the surface of the water the tubular spathe splits, and 

 the flower emerges, just floating above the surface. The 

 stigmas protrude between the perianth leaflets, and the flower 

 is ready for fertilisation. 



It will naturally be asked how this can take place, seeing 

 that the male flowers are matured close to the bottom of .the 

 water, often several feet below the level of the female flowers. 

 But Nature is always full of resources, and the plan which is 

 followed is as remarkable as any known in the whole range of 

 the vegetable world. When the male flowers are perfectly 

 mature the globular spathe which surrounds them splits 

 into three pieces, which hang downwards out of the way. 



