VEGETATION OF SWIFTLY FLOWING WATER 45 



million of these flying seeds, according to Professor Lloyd Praeger's 

 estimate. Another plant, sometimes called Bulrush, is the Sedge, 

 Scirpus lacustris. This, unlike most of the Sedges, is a leafless 

 plant. It has tall, smooth stems, sometimes six or eight feet in 

 height. The length of the stem varies with the habitat of the plant. 

 When growing by the edges of lakes it is short, sometimes not 

 more than six inches high ; in the water it grows very much taller. 



The Arrowhead (genus Sagittaria) and the Greater Water 

 Plantain (Alisma Plant ago) are often found growing in rivers, 

 not as near the banks as the upright plants. Both these plants 

 belong to the Alismaceae, and have rather a different type of 

 leaves from the upright type. They are not long and narrow, 

 but more lobelike and ovate in shape, approximating towards the 

 floating type. The Arrowhead is easily recognised by the shape 

 of the leaves, which develop in the following order. The first 

 leaves are submerged ; then come linear leaves, the upper part of 

 which floats on the water. Next floating leaves, in which an 

 ovate blade is developed, and lastly the triangular, deeply sagittate 

 leaves from which the plant is named. The leaves of the Water 

 Plantain have a somewhat similar development. The flowers 

 of the Arrowhead have three small, green sepals and three large 

 white petals, with a deep purple spot at the base of each. The 

 lower flowers are pistillate, and are on shorter stalks than the 

 upper staminate ones. The flowers of the Water Plantain in 

 general appearance are not unlike those of the Arrowhead, with 

 this distinction, that each flower contains both stamens and 

 carpels. The Flowering Rush may also be mentioned here, as it 

 is a semi-aquatic plant belonging to the Alismaceae, but it frequents 

 still rather than running wtaer. It is not a Rush at all, but was 

 probably thus named from the rush-like, leafless flower-stem. It 

 has rose-coloured flowers. With these plants there will be certain 

 Grasses, such as the Common Reed as it is called (Phragmites 

 communis) and the Reed Poa (Glyceria aquatica), and other well- 

 known plants, such as Docks, Spearworts, Yellow Loosestrife, etc. 



The vegetation of the banks of a river is therefore very varied, 

 so varied that it is difficult to fix on one dominant plant. The 

 Bur- Reed and the Reed Mace are generally about equal in num- 

 bers, whilst Phragmites communis often disputes the predominance 



