PLANTS FOR, 33 



plants, and are worthy of attention on that 

 account. They consist of three or four little 

 green leaves or fronds, from the under-side of 

 which they send down roots into the water in 

 which they float. If watched in the spring, one 

 of the little leaf-like bodies will be found to 

 contain two stamens and another a pistil. These 

 are the only flowers possessed by the little Duck- 

 weeds. In the Aquavivarium they will be found 

 very useful, as affording a screen from the sun- 

 light to the animals below. They also harbour 

 a number of microscopic creatures ; and it is 

 amongst the tiny forests which they form on 

 the surface of the water, that the microscopist 

 must hunt for some of his most valued game. 

 There are four species of Duckweed found in 

 our ponds. 



THE THREE-LOBED DUCKWEED (Lemna trisulca), 

 with pellucid, oblong, lanceolate fronds, and a 

 single root at one end. 



THE LITTLE DUCKWEED (Lemna minor), with com- 

 pressed, opaque, and nearly rounded fronds, 

 slightly convex beneath, and single roots. 



THE GIBBOUS DUCKWEED (Lemna gibba) has fronds 

 of the same shape as the last, but larger, and 

 nearly flat above, but gibbous and spongy 

 beneath, with single roots. 



THE MANY-ROOTED DUCKWEED (Lemna polyrhiza) is 

 known from the three lasb by the abundance of 

 its roots. Its fronds are not unlike those of the 

 last species, but are more round. It has not 

 been observed to flower in Great Britain. 



There are many other plants belonging to the 

 class of Endogens, which may, with great advan- 

 tage, be introduced into the Aquavivarium ; and 

 probably many like Yalisneria, which are stran- 

 gers to Great Britain, may be easily cultivated. 

 D 



