64 MR. C. BAILEY ON THE STRUCTURE ETC. 



seeing the plant in its station in the canal at Reddish, 

 near Manchester. The precise locality was not intended 

 to be published, but as the station seems to be well known 

 to so many local botanists, there is no further need to 

 suppress it. 



When I first visited the canal, on the 14th September, 

 1883, the Naias grew in an area of about a quarter of a 

 mile in length ; in some portions of this space it was the 

 prevailing plant, wholly covering the canal-bed, while in 

 other portions it was intermixed with Potamogeton rufes- 

 cens, P. obtusifolius, P. crispus, P. pusillus, Myriophyllum, 

 and Anacharis. Except in so far that the station, like 

 most canals, was an artificial one artificially supported, 

 there seemed nothing in the accompanying vegetation to 

 suggest that the Naias was not aboriginal. All the other 

 plants were of the prevailing canal character, the non- 

 native Anacharis being as much at home as any of them. 



The temperature of the canal water is, however, arti- 

 ficially raised by the discharge of hot water from boilers 

 and condensing-tanks attached to the cotton-mills and 

 other works which are erected on the banks of the canal. 

 In the declining evening of my first visit the water was 

 quite warm, say about 90° Fahr. This abnormal tempe- 

 rature must be looked upon as the important factor in the 

 struggle for existence maintained by this plant. In sub- 

 sequent visits to the canal the temperature of the water 

 was not met with so high as it was found on the first 

 occasion ; still, with the fitful discharge of hot water into 

 the canal at many points, its average temperature must be 

 many degrees above the normal point for the neighbour- 

 hood. It might have been expected that the vegetation 

 which grows in this tepid body of water would have shown 

 signs of luxuriance, but such does not appear to be the 

 ease. The most striking variation is met with in Pota- 



