192 



WATER PLANTS. 



Those alone are with propriety called Water Plants which 

 live in the water without any contact with the earth, or which 

 use their roots only to keep them firm in their situation. 

 Amongst other natives we have the Duck -weeds, so well 

 known as covering ponds and ditches, one is very small, 

 (Lemna minor) this is the most common. Another species, 

 (Lemna polyrrhiza,) is large and of a purple color underneath 

 its leaves. Lemna gibba is between these two in size and 

 thick, the under surface being puffed out it is not so common 

 as the last two. Lemna trisulca, or the Ivy-leaved Duck- weed, 

 is now and then found in similar places. The Pond-weeds, 

 (Potamogeton, Class 4,) are a very numerous family ; several 

 are common, and throng most streams and ditches, floating 

 under water, and bearing flowers in spikes. There are a few 

 more Water Plants in the twenty-first class, but these are 

 scarcely common enough to be more than alluded to. 



HORSE-TAIL AND CLUB-MOSSES. 



(Equisetum and Lycopodium.) 



1 2 



1. A, part of a barren frond of Equisetum arvense, or Field Horsetail, 

 B, fertile frond of ditto. C, one of the shields of the fruit removed. D. 

 .one of the seeds magnified. 2. A, a Clab-rnoss of natural size. B, one of 

 the leaves, showing beneath it one kind of fruit. C, one of the leaves 

 showing the other kind of fruit. D, the seed removed. 



The Horse-tails and the Club-Mosses are called allies to 

 the Ferns though very different in form. Those of the latter 

 tribe are not common except in mountainous countries nor is 

 their any thing remarkable in their appearance, as there is in 

 the Horse-tails. These have all hollow stems, with a certain 

 number of channels outside. They are set with joints, and 



