LEMNA GIBBA. GIBBOUS DUCK WEED.
LEMNA gibba; frondibus obovatis supra planis subtus hemisphasricis vesiculosis, radicibus subsolitariis.
LEMNA gibba. Linn. Sp. P L p. 1.377. With. Bot. A rr. ed. 4. ml. 2. p. 44. Hoffm. Germ. ed. 2.
ml. 1. P . I. p. 187. Willd. Sp. PI. ml. 4; p. 194. Smith, FI. Brit. p. 957. Engl. Bot.
t. 1233. Decand. Fl. Fr. ed. 3. ml. 2. p. 589- FI. Gall. Syn. p. 1 19- A it. Hort. Ketv.
ed. 2. ml. 5. p. 233. Pers. Syn. PI. ml. 2. p . 532. Hook. FI. Scot. P . I. p . ] 1 .
LEMNA minor ß. Huds. A ngl.p. 399-
HYDROPHACE monorrhiza, foliis pulvinatis, inferne convexissimis. Hall. Helv. n. 1898.
LENTICULA palustris major; inferne magis convexa, fructu polyspermo. Mich. Gen. 15. t. I \ . f . 2.
Class a n d Or d e r . D IANDRIA MONOGYNIA.
[N a tu r a l Or d e r . A ROIDEÆ: Seet. PISTIACEÆ, Rich., Hook. NAYADES, Juss.. Decand.
HYDROCHARIDIBUS AFFINIS, J à |
G e n . Ch a r . Perianthium simplex, membranaceum, urceolatum. Fructus, Capsula vel Utriculus monolocularis.
Ge n . Ch a r . Perianth simple, membranaceous, urceolate. Fruit, a Capsule or Utricule of one cell.
Ra d ix e fibra plerumque solitaria, simplicissima, duas
ad très uncias longa, filiformi, infra prope basin
egrediente, apice calyptrata.
Fron d e s aggregatæ, natantes, duas ad quatuor lineas
longæ, obovatæ, superne plan®, minutissime
atque obscure reticulat®, virides, subtus hemi-
sphæricæ, albidæ, vesiculoso-reticulatæ, areolis
magnis convexis : basi angustiore ad marginem
utrinque fissæ, rima vel gemmifera vel florifera.
Gemmæ cito explanatæ sunt in novas frondes, et
hæ frondes itaque prolifer®.
Flos minutus, hermaphroditus, vix ultra rimam frondis
produc tus.
P e r ia n t h ium minutissimum, ' suburceolatum, eroso-
truncatum, membranaceum, pellucidum.
St am in a duo ad unum latus germinis inserta, vel solitaria.
Filamentum pistillo longius, album, valde
succulentum. Antheræ didymæ, lobis rotunda-
tis, flavis, verticaliter dehiscentibus.
PlSTlLLUM : Germen subrotundum, obliquum, hinc pla-
niusculum : Stylus perianthio longior, albus : ■
Stigma dilatatum, concavum.
P e r ic a r p ium subrotundum, utriculatum, exsertum,
compressum, hinc planum, sæpe altero latere gib-
bosum, apice emarginatum, stylo brevi termina-
tum, mono-tetraspermum.
Sem in a transversim posita, ad basin utriculi vel peri-
carpii eorum medio affixa, elliptica, striata, dorso
præcipue. '
A l bum e n copiosum, carnosum.
E mbryo parvus, apice fissus fere in duos cotyledones,
hilo oppositus. Radicula ad hilum versa.
Root consisting o f a generally solitary,’ simple fibre,
two to three inches long, filiform, proceeding from
below and near the base of the plant, calyptrate
a t the extremity.
Fron d s clustered together, floating, from two to four
lines long, obovate, plane above, very minutely
and obscurely reticulated, green, hemispherical
beneath, and then white, vesiculoso-reticulated,
with the areoles large and c onvex: at the base
narrower, and cleft on each side at the margin,
which cleft either bears gemm® or flowers. The
gemmae are soon developed into new fronds, and
these fronds are again proliferous.
Flower minute, hermaphrodite, scarcely produced
beyond the cleft o f the frond.
Pe r ia n t h very small, somewhat pitcher-shaped, truncated
and erose, membranaceous and pellucid.
St am e n s , either two, arising from one side o f the germen,
or solitary: Filament longer than the pistil,
white, very succulent: Anthers didymous, with
the lobes rounded, yellow, opening vertically.
P is t il : Germen roundish, oblique, flattish on one
side: Style longer than the perianth, white:
Stigma dilated, concave.
P e r ic a r p roundish, utricular, exserted, compressed,
plane on one side, often gibbous on the other,
notched a t the apex, and terminated with a short
' style, one- or four-seeded.
Se ed s transversely placed at the base o f the utricule
or pericarp, affixed by their middle, elliptical,
striated, especially at the back.
A l bum e n copious, fleshy.
Embryo small, cleft at the apex almost into two cotyledon?,
opposite the hilum: Radicule directed
towards the hilum.
Fig. 1. Lemna gibba (nat. size). . Fig. 2. Proliferous plant (smagnified). Fig. 3. Flowering plant. Fi<r 4 Single
fI ond’ ™ wed from the underside. Fig, 5. Flower, the rima or cleft in the frond being laid open to show°it.
£ 2o - b- Flower separated from the frond. Fig. 7. Perianth broken away to show a pistil and stamen. Fig. 8.
Fructified plant. Fig. 9. Pericarp or Utricule. Fig. 10. Side view of ditto. Fiv. 1 1 . Seeds. Fi* 12 Single
seed. Fig. 13. Seed with part of the integument cut away, showing the brown tubercle attached^to the inner
coat or lining of the integument. Fig. 14. Seed cut open, showing the raphis and the embryo with its rima
or cleft; the raphis at f . a .:—more or less magnified.
In the earlier part of this work I have had the satisfaction o f figuring and describing the fructification of two
species of this curious genus, and of bringing forward many particulars not before known to botanists In the
month of July of last year, my friend Dr. Greville sent me flowering specimens and a sketch of the flowering
bonds of Lemna gibba ; and W. Wilson, Esq., of Warrington, communicated to me very perfect specimens in
fruit, gathered near his place of residence, in September of the same year: so that by the assistance of these two
able botanists, it is my own fault if I do not give satisfactory details of this species also;
The general character of the fructification and mode of growth of the fronds will be found- to be similar to that
of the Lemna trimica and L . minor. Here both Mr. Wilson and Dr. Greville observed, that when two stamens
were present, only one was protruded at a time; which goes far to confirm an idea previously hinted at,—that each
stamen is to be considered as a separate flower acting independently of the other, and comine to perfection at
a different period : the latter gentleman further observed, that each seed-vessel contained four seeds • whereas I
never found more than one in the former species. Micheli, indeed, had found as many as six seeds* in each Deri-
carp; but he has represented them erect—and they often appear erect, through the semi-pellucid covering • but a
f o u r t h " f i I '? " ' ,? at ‘“m “ 1 ‘“8tan“ th.® natural P°sition °f UK seed is transverse length, and that it is fixed by the middle on the underside to the bottom of the seed-vessel; and thewyi tahr er eognflryd f otorc eitds-
out of their direction by the smallness of the pericarp and the enlargement of the seeds (whenever there is more
than one), giving these latter an altered position : but the attachment is still the same, the raphis is stretched' and
even the soft pericarp is altered in its form, becoming gibbous; and its point of attachment Ts it were, excentral
The seeds themselves are very deeply striated, and the raphis communicates most distinctly with a brown tubercle
at one end ; and that brown tubercle is a portion of the inner lining of the integument, as may be seen at fig 12
wheie the outer portion of the integument is cut away, but the tubercle is not thereby removed. The albumen is
copious, and the embryo has so deeded a cleft; that it might without any misapplication of term be called dieoty"
I I B B I A C ef ,f“Srbeen seen ln l,he embry° of thls ° r some other species of the genus by Mr. Brown and
Mi Lindley: and the former acute observer has noticed its existence in the genus Arum. *
Lemna gibba is found floating upon the surface of pools and ditches, I believe, throughout Britain but is much
more common m England than in Scotland. TheLemnm generally are considered, like tile fesh-water c J n f Z f
the UnWh°1~ i r i " — ^ “ S d u r i n g t i i ^ f S
* I find them to vary from one to four.