ANACHABIS. 273 



adjust itself to any depth of water, so that its flower may float 

 on the surface, and afterwards contract, so as to draw down the 

 seed-vessel to ripen under water; and the Sugar Valisneria, 

 which is used to convey water to the sugar while undergoing 

 the process of refinement. 



I must here draw your attention to a new and extraordinary 

 plant belonging to this family. The bargemen on the Faxton 

 Canal have called it "Water Thyme," and botanists have 

 gifted it with a name a yard long, Anacharis alsinastrum, 

 (Plate XVII.,fig. 1). I found it first during the midsummer 

 holidays, when we were frequenting the neighbourhood of the 

 Learn for the double purpose of boating and shell-seeking. 

 The water weed that we drew out in the hopes of finding 

 molluscs upon it had whorls of leaves in three, with fringed 

 edges. In vain I searched "Withering for the plant, none 

 answering the description could be found. It grows in such 

 abundance in that sluggish stream that we frequently got our 

 oars fast in it. For some time I cast about in vain for a history 

 of my new friend, and at last I found all about it in a paper 

 in " Chambers' Journal," entitled " Alarming Invasion." It 

 appears that the plant was first discovered in a Berwickshire 

 Loch in 1842, by Dr. Johnston ; but its fame died away until 

 Miss ICirby found it in the canal near Market Harborough in 

 1 847. By this time the weed, growing with marvellous rapidity, 

 had made its way out of Dunse Loch, where Dr. Johnston had 

 found it, and was travelling down the Whiteadder to join the 

 Tweed. In the same season a portion of it was discovered in 

 a tributary of the Trent, and in 1849 it was " forming large 

 submerged masses of a striking appearance" in the stream 

 itself, and many of the canals communicating with it. A year 

 afterwards it was discovered in the Cam, and in the course of a 

 few months it so blocked up that river that extra horses had to 

 be yoked to the barges to draw them through its masses. This 

 plant, like the Frogbit, has its male and female flowers on 

 separate plants, one only of which is found in Britain, though 



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