WATEE-PLANTS. 



61 



a time become detached, rise to the top of the water, and float 

 there imtil they fertilise the female flowers with their pollen. 

 After the fertUisation the latter sink to ripen and to grow. 



The Vallisneria also increases by runners, somewhat similar 

 to the common strawberry. These offshoots run along the 

 bottom of the water until they begin to strike root in the soil. 



FiQ. W. Italian Water-weed, Vallisneria spiralis (Male Plant). 



and so a new plant is formed. This weed grows fairly well 

 in the sand at the bottom of an aquarium ; it will grow better 

 in pots in which there is some 4in. or 5in. of a good loam 

 covered by a layer of fine gravel ; but it will grow best of all in 

 a tank prepared for the purpose, and kept in a cool greenhouse. 



