LEMNACE^E. 23 



England. Rare in Scotland, where I have found it in Lochend and 

 Duddingston Loch, near Edinburgh ; and in Loch Gelly, Fife. Rare 

 and local in Ireland, where it is found about Limerick, and some places 

 in the east and north of the island. 



England, Scotland, Ireland, Perennial. Early Summer. 



Very similar to L. minor, but larger when full grown, being usually 

 about i inch long or even more, and usually with longer roots, but 

 the most striking difference is the convexity of the under surface, on 

 which a quantity of loose spongy tissue is developed so as to make a 

 section of the frond nearly semicircular. The flowers I have never 

 seen. 



Gibbous Duckweed. 



French, Lenticnle gonflee. German, Buclcch'ge Wasserlinse. 



Section IV.— SPIRODELA. 



Fronds floating, herbaceous, not apiculate or tailed, each giving rise 

 to a tuft of numerous root-fibres, furnished with membranous-edged 

 baso-lateral clefts from which young fronds are produced, which remain 

 sessile and attached only for a short time to the parent frond ; cells of 

 the epidermis bounded by sinuous lines. Flowers from a cleft in the 

 margin of the frond ( ?). Ovary with 2 ovules. Fruit unknown. 



SPECIES IV.-LEMN A POLYRRHIZA. lAnn. 



Plate MCCCXCVII. 



Heidi. Tc. Fl. Germ, et Helv. Vol. VII. Tat). XV. Fig 17. 



Billot, Fl. Gall, et Germ. Exsicc. No. 2941. 



Splrodela polyrrkLza, Schleid. Kunth. Enum. PI. Vol. III. p. 7, 



Fronds floating, opaque, thick, flat above, very slightly convex 

 beneath, suborbicular, entire, not tailed, not apiculate, marked with 

 numerous vems diverging from the point where the roots are pro- 

 duced ; the young fronds sessile, each frond giving rise to a tuft of 

 root-fibres ; the under side without spongy tissue. 



In ponds and ditches. Not uncommon, and generally distributed 

 in England, reaching northward to York and Lancasliire. Formerly 

 found at Duddingston Loch, near Edinburgh, from whence I have seen 

 specimens collected by Dr. Philip Maclagan, but where I have never 

 succeeded in finding the plant. Mr. H. C. Watson gives the west 

 lowland province as one in which it occurs, but I am unable to say in 

 which of the three counties, viz. Ayr, Renfrew, or Lanark, it has been 



