182 TRANSACTIONS OF THE [Sess, lxxvii. 



In the district round Edinburgh Stratiotes has been 

 present at Duddingston Loch, Lochend, and the marl pit 

 near Davidson's Mains, from all of which it has now quite 

 disappeared. In 1909 Mr. W. Edgar Evans (5) found it in 

 a pool between Haddington and Morham. The records for 

 Duddingston Loch go back to 1840. Mr. Wm. Evans, to 

 whom I am indebted for much information about the 

 Stratiotes localities near Edinburgh, does not know at 

 what time it disappeared from Duddingston. 



In the marl pit near Davidson's Mains Stratiotes was 

 present until a few years ago, but there is now no trace 

 of it, partly, no doubt, owing to the spread of Equisetum 

 limosum, Linn., over the pond, more probably because of 

 the depredations of collectors. 



At Morham the only associated plant is Lemna minor. 



Outside of the Edinburgh district Stratiotes has been 

 found at Loch Rescobie, the Loch of Forfar, the Loch of 

 Clunie, and in ponds in vice-counties 83, 84, 90, and in 

 Perthshire. In all of these places Professor Trail (6) 

 records it as " introduced." 



The presence of marl in the pit at Davidson's Mains and 

 at Loch Rescobie suggests one condition for the success of 

 Stratiotes. The lime from the marl probably neutralises 

 the humic acids of the ponds sufficiently to permit 

 Stratiotes to thrive. The water in the Norfolk Broads 

 must also be to some extent charged with lime from the 

 underlying geological formation. 



Mr. Gentles tells me that marl was once raised from the 

 loch at Ochtertyre, which is near Blackbank Pond, and 

 my analysis, of water kindly sent by Mr. Gentles from 

 Blackbank Pond, has revealed 13 grains of carbonate 

 of lime per gallon. 



Stratiotes thus appears to thrive in water more or less 

 richly charged with lime. Experimental ecology, by 

 introducing plants into probably favourable situations, 

 might confirm relations to environment such as this of 

 Stratiotes to lime. 



In all of the situations mentioned, however, the lime is 

 present in comparatively small proportions. An experi- 

 ment worth trying would be the introduction of Stratiotes 

 into such a loch as that at Carlingwark, Dumfriesshire, 



