132 
CLIX. LEMNACE^. 
[Lemna. 
Fronds with one or more roots from the under surface; 
flowers lateral . . . . . . . . i. Lemna 
Fronds with no roots; flowers on the upper surface . . 2, Wolffia 
1. LEMNA, Linn. 
Fronds flat with i or more roots. Flowers i or more in a spatlie 
on the edge of the frond. Species about 12, whole world. 
Koot one. 
Fronds elliptic asymmetric . . . . . (i) L. paucicostata 
Fronds ovoid acuminate . . . . . (2) L. tenera 
Roots several. 
Frond orbicular . . . . . . . (3) L. polyrrhiza 
(1) L. paucicostata Hegelmaier, Lemnacece, 139, L 8; Hook. 
fiL F.B.L vi. 556; RidL Mat. iii. 52. L. minor Gri§. Noiida;, 
iii. 216. 
Roots solitary, frond asymmetric elliptic or ovate, *12 in. Icng, 
light green. Spathe truncate. Stamens i or 2. Pistil very short, 
flask-shaped, truncate. Ovules solitary. Hab. Ditches and ponds. 
Singapore, Garden Lake; Angmokio. Pahang, Pekan. Malacca, 
well in Residency garden. Province Wellesley, Permatang Bertam. 
The commonest species. Distrib. Tropics generally. 
(2) L. tenera Kurz, Journ. As. Soc. Beng. xl. 1871, ii. 78; 
Ridl. Mat. iii. 52. 
Root solitary. Frond thin ovate acuminate or lanceolate with 
I or 2 young ones budding off from one side, -25 in. long. Flowers 
not seen. Hab. In ditches and ponds. Singapore, Galang; Telok 
Kurau (Ridley). Bindings, Bruas. Distrib. Pegu. 
(3) L. polyrrhiza Linn. Sp. PI. 970; Hook. fd. l.c. vi. 557; Ridl. 
Mai. iii. 53. L. major Griff. Notulce, iii. 216; Ic. PI. .Is. t. 264. 
L. orbiculata Roxb. FI. Ind. iii. 565. 
Roots several, *5 in. long. Frond orbicular or ovate, rather 
thick, *13 in. long, green above, purple beneath. Spathe 2-lipped. 
Stamens 2; ovules i or 2. Hab. Ditches, not common. Singapore, 
ditches by Alexandra Road. Distrib. Wdiole world. 
The greater Duckweed. 
2 . WOLFFIA, Horkel. 
Fronds minute, dark green, rootless. Flowers on the upper 
surface. Spathe o. Anthers sessile, i-celled. Style short; stigma 
depressed. Ovule i. Species 12, whole world. 
(i) W. arhiza Winm. FI. Schlesw. 140; Ridl. Mat. iii. 53. 
Lemna arhiza Linn. Mantiss. 294. Grantia globosa Griff. Nottdev, 
iii. 229; Ic. PL t. 267, fig. 2. 
Fronds globose, green, microscopic. Hab. In ditches and wells. 
Singapore, Tanglin. Malacca, in a well at the Residency (Ridley). 
Distrib. Europe, India, Java. 
Tliis plant occurs mixed \vith Lemna but is not common, and when it 
occurs it is often immensely abundant for a time, then disappearing. 
