WEEDS OF PONDS, RIVERS, DITCHES 339 



present. The inflorescences are terminal, reddish- 

 brown clusters or cymes. 



S. TaberncemontaniGmzl. is a sub-species of the above, 

 with glaucous stems. 



Sedges. -Many of these plants are found in marshes 

 and ditches and on the margins of ponds and rivers. 

 They much resemble grasses in general appearance, but 

 the stems are usually triangular in section, and the 

 leaf-sheaths are entire, not split, as in most grasses. 

 The flowers are unisexual and in spikes ; the male 

 flowers have three stamens and no perianth ; the female 

 flowers have a peculiar bottle-shaped perianth, in which 

 is the ovary, with its two or three projecting stigmas. 

 The fruit is a small, three-angled nut. 



Common species which may be described as weeds 

 of the margins of ponds, river-banks, and ditches are 

 Carex ampullacea Good., C. vesicaria L., C. paludosa 

 Good., and C. riparia Curt. These grow from i to 3 

 feet high, with broad, grass-like leaves, and have creep- 

 ing or tufted rootstocks. 



GRAMINE.E 



The Reed (Phragmites communis Trin.) is a grass 

 which occurs in shallow water at the edges of lakes and 

 streams and in ditches throughout the country. It is 

 useful for bedding of animals and for thatching. The 

 rootstock is much branched, often forming a dense, 

 mat-like growth under water, some of the rhizomes 

 extending 20 or 30 feet. The erect stems are round, 

 6 to 10 feet high, with broad flat leaves usually about 

 an inch wide, and of ashy-green colour beneath. The 

 panicle is diffuse, 6 to 12 inches long, with purple, 

 shining, three- to six-flowered spikelets. 



