1248 
LEMNACE^ OR DUCKWEEDS, 
appearance from the Australian one, the little flowers burst from 
a cavity on the upper surface of the frond without any spathe or 
bract, revealing a solitary anther, and a short style with a broad 
stigma. 
Of the genus Lemna, the Baron gives for Australia five species, 
three of which, L. trisulca (Linn.), L. minor (Linn.), and L. giliba 
(Linn.), have only one root or fibre; whilst L. oligorrTiiza (Kurz), 
which the writer collected in Parramatta, has five roots or more, 
and L. polgrrhiza (Linn.) a cluster of many. Three species are 
recorded from Port Jackson, one from W. Australia, and one 
from some part of N.S. Wales not specified. In Lemna the 
flowers issue from a fissure in the margin of the frond, the 
anthers have two distinct cells, and the style is generally short. 
Two species of the genus are described shortly in R. Brown’s 
Prodomus ; the others have been discovered of late years, but 
much remains to be learned respecting their peculiarities and 
distribution. Per.sons desirous of studying these minute plants 
should collect them in some suitable vessel with the water in 
which they are found, and transfer them to an ordinary tumbler 
for careful examination. Some of the species possess extra- 
ordinary vitality. They will keep alive and grow for some time, 
so that a good opportunity is afforded for observing the mode and 
time of flowering, as well as the marks which distinguish one 
species from another. Some writers have noticed the relation- 
ship of Lemnacece to Cryptogams (see Plantes Cryptogames dii 
Nord by Lesmazieres), and others have recognised their affinity 
with the Arum family (Sach’s Text Book of Botany). Brown 
placed them provisionally with Hydrocharidece, but now they are 
i-egarded as a distinct order. Whilst the simplest of all pheno- 
gamous plants, they occupy an important though humble place in 
the economy of nature. Some of the species afford nourishment 
to ducks and geese, as well as protection to various kinds of 
infusoria, and, like other green plants, convert carbonic acid gas 
into air adapted to respiration. This is said especially of L. 
minor, which in some seasons increases in a surprising manner, 
