FROG-BIT TEIBE 207 



collegians were, by its masses, prevented from rowing, as it not only impeded 

 the course of a boat, but would even overturn it ; while the most skilful 

 swimmer became entangled in its toils. Bathers found it clinging to their 

 limbs "like scratch-weed"; and in more than one case fatal accidents 

 ensued in consequence of its intertwining branches. It was afterwards 

 observed at Ely, where it occasioned immense trouble by choking up the 

 railway-dock; and an engineer found that, in the year 1852, it had so 

 hindered the drainage in the fenny parts of Cambridgeshire and Huntingdon- 

 shire, that it was equivalent to a rise of one foot in the outlet level. Mr. 

 Marshall of Ely, who gave great attention to the progress of this weed, and 

 who, in 1854, published a pamphlet recording his observations, said : " The 

 specific gravity of this plant is so nearly that of water, that it is more 

 disposed to sink than float ; and the cut masses may be seen under water, 

 either on or near the bottom, rolling over and over, like woolpacks, clinging 

 to everything they meet with, and accumulating in great quantities in locks 

 and bridges, and grounding in shallow water. Its mode of growth may be 

 best seen in still and shallow waters, where it seems to spring first from the 

 two sides and the bottom, meeting at length in the middle, and completely 

 filling up the watercourse, as I have seen in some cases, almost to the exclu- 

 sion of the water." 



Since the third discovery of the Anacharis in 1847, the plant has been 

 found making its progress every season into some new or hitherto unobserved 

 locality; and, during the course of the year 1855, it was seen for the fii"st 

 time growing in abundance in a land-drain at Weybridge and Walton, which 

 empties itself into the Thames, blooming there in profusion. 



None of the theories respecting the introduction of this plant into the 

 Dunse loch are very satisfactory ; but when once the weed reaches the 

 waters in the centre of England, its dissemination ceases to be a mystery. 

 Mr. Marshall, in a communication made to the Gardener's Chronicle, in 1853, 

 says : "In the letter which I published last year on this remarkable plant, 

 I stated that when once introduced, it would, in a few years, inoculate any 

 connected water system from one end to the other. I added, that if anyone 

 would look at a good map of England, it would appear that there was hardly 

 a spot so well situated as a centre from which to inoculate our English rivers, 

 as Eugby, or the Watford locks near the Crick railway, where it was found 

 in profusion. From such a point, situated at an altitude above the sea of 

 350 feet, and very nearly at the line of water-shed which divides England 

 into the river-basins of the Severn on the west, the Trent on the north, the 

 Ouse on the east, and the Thames on the south ; a few detached pieces 

 travelling diff'erent ways would enter the Severn through the Avon, by the 

 way of Rugby and Warwick ; the Thames, through the Cherwell ; the Nene, 

 above Northampton; the Ouse at Buckingham; the Welland at Market 

 Harborough ; the Trent by the Anker, Tame, and Soar ; from the Soar it 

 might enter the Witham, through the Grantham Canal, and thence by 

 Lincoln into the water-courses which drain the fens of North Lincolnshire, 

 and which now are so full of this weed ; while, at the jimction of the Trent 

 with the Humber, that large river and its tributary streams might have been 

 visited by this troublesome emigrant." 



