292 LEMNACEJ]. 



First record; Irvine, about 1830. Usually entirely submerged, and 

 forming a more or less complete subaqueous stratum beneath the 

 floating species. J. de C. Sowerby says it is not rare ' in the vicinity 

 of London ' in flower ; Mag. Nat. Hist. i. 290. 



706. Xi. minor, L. Duckweed. 



Cyb. Br. iii. 27. Syme E. B. ix. t. 1395 (bad figure, though the original 



drawing for E. B. 1045 is good). 

 Floating on stagnant water : very common. P. ? June, July. 

 Throughout all the districts. 

 VII. Common about town. Hornsey Wood Ponds. Hackney Wick. Isle 

 of Dogs. 

 First record : Irvine, about 1830. It is frequently found in flower. There 

 are good figures of the flowers in Hook. Curt. vol. iv. 



707. Ii. gribba, L. 



Cyb. Br. iii. 27. Syme E. B. ix. t. 1396. 



Floating on ditches and ponds ; rather common. P. ? June, July, 

 I. Eastcott ; Farrar. Near Potter's Bar Ey. Station, abundant. 

 II; Staines Moor. Staines Common. Ditch by side of Queen's Eiver, 

 Hampton, abundant. 



III. Eoxeth; Hind, in Fhyt.N.S. iv. 116. Cran on Hounslow Heath. 



Whitton, abundant. About Twickenham in several places. Isle- 

 worth. 



IV. Silk Bridge near the Hyde, Hendon ; Irv. MSS. Harrow Weald. 

 V. Ponds on road from Harrow to Greenford ; Farrar. 



VII. Hackney Wick, abundant, 1867. 

 First record: Irvine, about 1830. Much overlooked ; it usually, though 

 by no means always, excludes other species of Lemna, covering the 

 whole surface of the water with a very dense sheet of vegetation. The 

 flowers are well figured in Hook. Curt. vol. v. 



708. Ii. polyrrhiza, L. 



Cyb. Br. iii. 28. Syme E. B. ix. t. 1397. 



Floating on ponds and ditches ; rather common. P. ? Flowers not yet 



seen in Britain. 

 I. Feeder to Elstree Eeservoir. Near South Mims. 

 II. Staines Moor. Staines Common. Bet. Hampton and Sunbury ! ; 

 Newb. 



III. Hounslow Heath. Isleworth, sparingly. Ponds, Harrow ; Hind, in 



Thyt. N. 8. iv. 116. 



IV. Hampstead Heath ; Herb. Hardw. Pond bet. Finchley and Hendon ! ; 



Newb. In the Brent ; Farrar. 

 V. Ealing Common, abundant ! ; Newb. 

 VII. Hornsey; Varenne. Bishop's Walk, Fulham; Hei-b. Hardw. Ser- 

 pentine ; Herb. Devon Institution, Exeter. In the Hampstead Ponds, 

 abundant; W. G. Smith in Science Gossip, vol. i. 



