706 



Letter I. 



A remarkable plant has recently made its appearance in the 

 rivers Ouse and Cam, and already abounds to such a degree as not 

 only to impede navigation, but, what is of far more importance in this 

 fen country, threatens to injure our drainage. 



It occurs in dense, tangled, submerged masses, of considerable ex- 

 tent, and is so heavy that when cut, instead of rising to the surface 

 and floating down to sea, like other weeds, it sinks to the bottom. It 

 is this property which is likely to make it injurious to drainage. The 

 intruder is so unlike any other water-plant, that it may be at once 

 recognized by its leaves growing in threes, rouud a slender, stringy 

 stem. The watermen on the river have already dubbed it " water- 

 thyme," from a faint general resemblance which it bears to that plaut. 



That it is new to our rivers here is certain. Watermen and fisher- 

 men pronounce it to be (as I heard one of them call it the other day) 

 " a furreigner." 



Who the stranger is, whence he came, and how he got here, are 

 questions of considerable scientific interest ; but by what means he is 

 to be got rid of is the practical question. With your permission I 

 will discuss these points in another communication. 



Letter 2. 



I now trouble you with the second part of my communication on 

 the subject of this new water-weed, in which I promised to discuss, 

 who the stranger is, whence he came, how he got here, and by what 

 means he is to be got rid of. 



With respect to the first question, it is sufficient to say that it is 

 the Anacharis Alsinastrum of your eminent townsman, Mr. C. C. Ba- 

 bington (to whose accurate labours our indigenous botany is so much 

 indebted), who so named it in 1848. 



The following is a short account of what we know of the plant : — 



It a))pears that it was first found in this country on the 3rd of Au- 

 gust, 1842, by Dr. George Johnston, of Berwick-on-Tweed, in the 

 lake of Dunse Castle, in Berwickshire. The lake is situated upon 

 a tributary of the Whitadder River, which flows into the Tweed. 

 Specimens were sent at the time to Mr. Babington ; but the discovery 

 was lost sight of, and the interest in it died away until the autumn of 

 1847, when it was again discovered, by Miss Kirby, of Lubbenham 

 Lodge, in reservoirs adjoining the Foxton Locks, on the canal near 



