705 



of the theft; and if we discovered how he entered the house we may 

 fairly and wisely set our wits to work to blockade that entrance. 

 Now T think it can hardly be denied that this precise, and exact, and 

 laborious tracing out of the cause of the straw-blight, — this finding 

 out of the thief, and how he entered, — is in itself a preliminary step 

 to a cure ; and such discoveries are not useless because unaccom- 

 panied by an empirical announcement of a cure. 



Edward Newman. 



Devonshire Street, Bishopsgate, 

 September, 1852. 



Excessive and noxious Increase of Udora Canadensis (Anacharis 

 AlsinastrumJ. By W. Marshall, Esq. 



I SEND you a series of four letters on the Anacharis Alsinastrum, 

 which I have just had re-printed from our local paper, for private 

 circulation. The sudden appearance of the plant in the Cam, and its 

 most prodigious powers of increase, have invested it with much local 

 interest, seeing that in this fenny country we can only exist by main- 

 taining a free and unimpeded drainage. 



The first two letters only contain a short history of the several dis- 

 coveries of the plant in this country, for the greater part of which I 

 am indebted to the pages of the ' Phytologist.' 



The third letter is devoted to the peculiar behaviour of the intruder 

 in our rivers here, and the mischief which has already ensued to na- 

 vigation, drainage, boating, swimming, angling, and fishing. The 

 fourth discusses the questions, whence it came, how it got to Britain, 

 how it reached the Cam, and how it is to be got rid of. If your read- 

 ers should not agree in my view of its first introduction, an opportu- 

 nity will be aflforded of discussing and clearing up the matter. 



I think the undoubted fact of its being an importation into the 



Cam so recently as 1848 — 1849, and its marvellous development since, 



a most interesting feature in its history, because it shows the mischief 



the plant is capable of doing in a very limited time, and goes a long 



way to prove that it cannot possibly be indigenous, because such a 



plant could never have been overlooked. 



W. Marshall. 

 Ely, September 16, 1852. 



VOL. IV. 4 X 



