Aquatic Plants Worth Cultivating 
W. A. Poyser 
Hammond, Indiana 
1. THe Froatine Fern. 
Ceratopteris thalictroides, the floating 
or water-fern, is an anomaly among 
ferns and one of the few truly aquatic or 
hydrophytic species. A plant of quiet 
waters of the tropics, it extends around 
the world, occurring in the United States 
in Florida and Louisiana. The plant is 
usually a rosette of simple (in young 
specimens) or deeply lobed or divided, 
more or less bluntly triangular, or del- 
toid leaves or fronds; the blade is suc- 
culent in texture with a thick stem filled 
with air-cells; the fertile or spore-bear- 
ing leaf is erect, longer and more divided 
into narrow segments, the leaf tissue 
being sacrificed to spore-production. 
Aside from propagation by means of 
spores, the species produces new plants 
freely from proliferous buds at the edges 
or occasionally on the surface of the 
leaves, depending more upon this method 
than upon the more uncertain sexual proc- 
Phe 
ually of new plants by gemmae, bulblets 
ess. viviparous production, asex- 
or buds is not uncommon among plants of 
the lower orders. In cultivation the float- 
ing-fern seldom produces fertile or spore- 
bearing fronds or leaves, probably be- 
cause it is usually grown in water too deep 
to permit the roots to reach the soil. 
While as an oxygenator the floating- 
fern is of no value to the aquarist, as a 
surface plant it forms a pleasing addition 
to a collection. Given a sunny position in 
a warm room, it responds with a wealth of 
cheerful light green, and multiplies rap- 
idly. 
tentment with such a surface covering, 
The fish seem to find a certain con- 
and vegetarian species are not averse to 
an occasional nip at the succulent leaves. 
2. Tue Duckweebs. 
Upwards of two thousand years ago 
there liyed in Greece a certain philoso- 
20 
pher, who, like Pliny and Aristotle, de- 
voted a portion of his time and talent to 
the study of nature. The savant to whom 
I refer was Theophrastus, who wrote a 
treatise on plants somewhere about B. C. 
300. 
with an aquatic plant to which he gave 
This same Greek was acquainted 
the name Lemna. The name was _ possi- 
bly suggested to him by the little island 
of Lemnos, in the A*gean Sea, apparently 
Tisig 
now uncertain as to what the precise plant 
floating on the water like a leaf. 
was to which he gave the name, it might 
have been a “duckweed” or something else. 
More recently this name has been given to 
a group of aquatic plants known to every 
one who wanders by puddles or ponds. 
Several species of duckweed are com- 
mon to both United States and Europe. 
There are no real stems and no real leaves, 
but the whole plant consists of little green 
fronds which look like leaves and of which 
one alone constitutes a plant or two or 
three adhering together, with one or two 
thread-like rootlets the 
underside. The fronds multiply by young 
ones growing from the edges of those 
hanging from 
that are mature. The flowers, very sim- 
ple and minute and rare, are produced 
from cracks or fissures in the edge of the 
frond. 
all our local species except Wolffia Co- 
In general this description covers 
lumbiana. 
The Lesser Duckweed (Lemna minor) 
is our most common species and consists of 
a tiny oval or round frond, two to five 
diameter, with a single 
millimeters in 
rootlet. Lemna perpusilla too has a sin- 
gle rootlet, but the frond is smaller, aver- 
aging about the size of that of the small- 
est Lemna The attractive 
species, as well as the largest, is Lemna 
The are oblong and 
pointed, growing at right angles in two 
The Greater Duckweed, Lemna 
since 
minor. most 
trisulca. fronds 
planes. 
polyrhiza of Linneus, has long 
been placed in a separate genus of the 
family and is now called Spirodela poly- 
