429 THE DUCKWEED FAMILY. [Lemna. 
Fronds broadly ovate, under 3 lines diameter. 
Fronds rather thick, slightly convex underneath . : . 2, minor, 
Fronds very thick and convex underneath ‘ . & LL. gibba. 
Roots none. Fronds minute, with ae pes on the upper sur- 
face. ; é , : . 5. DL. arrhiza. 
1. L. trisulca, Linn. le 946), nyt leaved D.—Fronds very dif- 
ferently shaped from those of the other species, and much thinner, 
They are usually near 6 lines long and about half that breadth, 
thin, narrow, and minutely toothed at one end, and ending in a 
little stalk at the other, with 2 young ones usually growing from 
opposite sides near the base, and a single root from underneath. 
Flowers of L. minor. | 
On ponds and still waters. One of the common species on the Con- 
tinent, but less so in Britain, especially in the north. Fl. summer, but 
very 7 arely Yy. 
2. L. minor, Linn. (fig. 947). Lesser D.—Fronds usually about 2 — 
lines long, broadly ovate or orbicular, cohering 3 or 4 together, with 
1 root under each but without any stalk, quite entire, and of a rather 
thick consistence. Ovary with a single ovule. 
On ponds and still waters, throughout the range of the genus, and 
generally the commonest species, often covering the water to a great 
extent. FJ. summer, commencing early, and more found in that state than 
any other species. [The flowering patches may be discerned by their 
yellowish hue.] , 
3. L. gioba, Linn. (fig. 948). Gibbous D.—Fronds shaped like those 
of LZ. minor, but rather larger and much thicker, flat above, spongy, and 
almost hemispherical underneath, with a single root to each. Stamens 
2. Ovary with 2 or more ovules. 
With the station and range of ZL. minor it is everywhere less common. 
Local in England and Ireland, and rare in Scotland. Fl. summer, very 
rarely. 
4. L. polyrrhiza, Linn. (fig. 949). Greater D.—¥Fronds larger than 
in any other species, attaining 3 or 4 lines diameter, broadly ovate or 
orbicular, rather thick, with a cluster of roots under each one. Flowers 
of L. gibba. 
As widely dispersed as the other species, and rather more frequent 
than L. gibba, except in Scotland. The flowers have never been observed 
in Britain. 
5. L. arrhiza, Linn. (fig. 950). Rootless D.—Fronds rather thick 
and swollen on the underside, but much smaller than in any other 
British species, only half a line long and rarely emitting any root. 
Anther solitary, globose, sessile. Ovary with a single ovule, the flower 
and fruit issuing from the upper surface, not from the edge of the 
frond as in the other species, on which account this one has been 
separated as a genus under the name of Wolfia. 
On ponds and still waters, common in the warmer regions of Asia 
and Africa, and perhaps in South America, more rare in Europe. 
In Britain flowerless, and confined to the south-eastern counties. 
Fl. summer. 
PTA Oe 
