LEMNACES. 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 + 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. 
Gibbon’s Duckweed. 
French, Lenticule gonflée. German, Buckelige 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.-LEMNA POLYRRHIZA. Linn. 
Prats MCCCXCVII. 
Reich. Ic. Fl. Germ. et Helv. Vol. VII. Tab. XV. Fig. 17. 
Billot, F). Gall. et Germ. Exsice. No. 2941. 
Spirodela polyrrhiza, Schleid. Kunth. Enum. PI. Vol. II. p. 7. 
Fronds floating, opaque, thick, flat above, very slightly convex 
beneath, suborbicular, entire, not tailed, not apiculate, marked with 
numerous veins 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. 
Tn ponds and ditches. Not uncommon, and generally distributed 
in England, reaching northward to York and Lancashire. 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 
