24 ON NAIAS GBAMINEA DEL., VAE. DELILEI MAGNUS. 



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, artificially 

 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 temperature must be looked upon as the important 

 factor in the struggle for existence maintained by this plant. In 

 subsequent 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 neighbourhood. 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 

 case. The most striking variation is met with in Potamogeton 

 crispus, which becomes dwarfed, particularly in stations where 

 there is an inflowing stream of warm water. 



Two other plants which grow in the same canal ought to be 

 noticed in this connexion. The first of these is the Cham Braunii 

 Gmel., which the Messrs. Groves figured and described in the 

 ' Journal of Botany ' for January, 1884, t. 242, p. 3. This plant 

 affects the edges of the canal, but it also occurs in the deeper 

 water of the centre, where it is more liable to be cut down by the 

 passing barges. Another interesting plant grows with the Chara, 

 whose identity is by no means settled, and it may prove worthy of 

 a more detailed notice viz., a species of Zannichellia. 



Mr. Whitehead had mentioned to me, on the occasion of our 

 joint visit, that Z. palustris had been recently found in the canal 

 and as it was an infrequent plant in the district surrounding 

 Manchester, I was anxious to procure specimens, although it 

 involved a moonlight search. It was while hunting for this plant 

 that, unknown to myself or to my companions, I collected the Chara 

 in the darkness ; the specimens were very fragmentary, but from 

 them Mr. Arthur Bennett determined the plant to be the Chara 

 Braunii, new to the British Flora. In justice to Mr. Whitehead it 

 ought to be stated that he and Mr. Armitage had collected it in 

 the same station a fortnight or so prior to my visit. 



The Zannichellia grows in the soft mud in the shallower parts 

 of the canal, with Chara Braunii and Potamogeton pusillus; it also 

 occurs in places where the water scarcely covers it. It would 

 appear to flower and fruit in the mud as well as in the water, but 

 the fruits which are produced in mud are of a very pale yellow- 

 green, on account of their imperfect exposure to the light. From 

 the dwarf, creeping, habit of the plant it seems to have an affinity 

 with the form of Z. palustris, named Z. repens Bcenningh. The 



