FEESH-WATEE AQUAEIA. 



Fig. 69. Greater Duckweed (Lemna 

 polyrhiza). 



not at all in Britain. In -winter ttey sink to the bottom of 



tte water. 



The Greater Duck- 

 weed (Lemna polyrhiza) 

 (Fig. 69) is rather larger 

 than the rest of the 

 duckweeds. Its fronds 

 or leaves are nearly 

 round, about ^in. in 

 diameter, thiokish, dark 

 green above and pur- 

 ple below, each frond 

 having a number of 

 little roots or fibres 

 growing from beneath. 

 This is a rare plant. 



The Thick Duck- 

 weed (Lemna gihha) 



(Fig. 70) has fronds almost round, about |in. in diameter, 



bright green in colour, flat above 



and round beneath. The fronds 



have only one fibre each. This 



plant is occasionally found growing 



with other duckweeds upon still 



water. 



The Lesser Duckweed (Lemna 



minor) (Fig. 71) is the commonest 



of all: the fronds are small, ovate, 



light green above and a lighter 



green below, with one rootlet to 



each frond. 

 The Ivy-leaved Duckweed (Lemna 



trisulca) (Fig. 72) is fairly common 



on lakes and ponds. It is about 



Jin. long, elliptical, thin, serrated 



near one end, and of a light green 



colour. The young fronds grow at 



right angles to the old ones, and each frond has one fibre. 





Fig. 70. Thick Duckweed 

 (Lemna gibba). 



