378 JSTAIADACEJE. {PoUmogetm. 



First found in Ireland by "W. H. Harvey, at Castleconnell, in 

 1834. 



P. Bdbingtonii Ar. Bennett — P. longifoKus Bab. — P. lucms x 

 prcelongus. — To this hybrid should probably be referred the Lough 

 Corrib plant figured in English Botany Supp. tab. 284'j under the 

 name P. longifoKus Gay. Only a single floating fragment seems to 

 have been picked up by Mr. J. Bell in 1835, and although it differs 

 in several points from admitted specimens of this hybrid, all these 

 differences, Mr. Arthur Bennett states, may be explained by assum- 

 ing the fragment to have floated for some time. Mr. Bennett also 

 mentions {Journ. of Bot. iSg^, p. 20^) that he has specimens of both 

 P. luoens and P. prcelongus from the same lake, and suggests the 

 name P. Babingtonii for this hybrid, P. longifolius being already 

 occupied. 



10. P, perfoliatus Linn. — Perfoliate Pond-weed. 



Districts I. 11. III. IV. V. VI. VII. VIII. IX. X. XL XII. 



Lat. 51i°-66i°. Throughout Ireland. Type, British. 



Lowland. Rivers, lakes, ditches, &c. ; frequent. Fl. June- 

 July. 



11. P. crispus Linn. — Curled Pond-weed. 



Districts I. II. III. IV. V. VI. VII. VIII. IX. X. XL XH. 



Lat. 51i°-56i°. Thi-oughout Ireland. Type, British-English. 



Lowland. Lakes, rivers, canals, and ditches; frequent. Fl. 

 June-July. 



j!^ot common in some parts of Ireland, as in Kerry and Donegal. 



Var. SEEEAius Suds. — XII. In the Bann near Portglenone, 

 Antrim and Derry {Stewart) : Flor. N.-F. 



P. undulatus WoLfg. — P. perfoliatus x crispus. — XII. Sis-mile 

 Eiver above Templepatrick, Antrim {Stewart) : S.SfP. i8g^. 



The Antrim plant is nearest to var. Jacksoisti Fryer, fide Ar. 

 Bennett: Journ. of Bot. i8g4, p. i^/f.. 



12. P. densus Linn. — Opposite-leaved Pond-weed. 



Districts I. II. III. IV. V. VI. VII. _____ 

 Lat. 62°-53^°. Southern half of Ireland. Type, English. 



Lowland. Rivers, ditches, canals, &c. ; rare and local. Fl. 

 July-August. 



