jlemna g ib b a . g ib b o u s d u c k w e e d .
LEMNAgibba; frondibus obovatis supra planis subtushemisphasricis vesiculosis, radicibus subsolitariis.
LEMNA gibba. Linn. Sp. PL p. 1377. With. Bot. Arr. ed. 4. ml. 2. p. 44. Hoffm. Germ. ed. 2.
ml. 1. P . I. p. 187. Willd. Sp. PI. ml. 4; p . 194. Smith, Fl. Brit. p. 957. Engl. Bot.
t. 1233. Decand. Fl. Fr. ed. 3. ml. 2. p. 589. Fl. Gall. Syn. p. 119. Ait. Hort. Kezo.
ed. 2. ml. 5. p . 233. Pet's. Syn. P i. ml. 2. p . 532. Hook. Fl. Scot. P . I . p . l i .
LEMNA minor ß. Ends. Angl. p. 399-
HYDROPHACE monorrbiza, foliis pulvinatis, inferne convexissimis. Hall. Helv. n. 1898.
LENTICULA palustris major ; inferne magis convexa, fructu polyspermo. Mich. Gen. 15. t. \ \ . f . 2 .
Class an d O rd e r . DIANDRIA MONOGYNIA.
[Natural Ord e r . AROIDEiE: Sect. PISTIACE/E, Rich., Hook. NAYADES. Juss., Decand.
HYDROCHARIDII3US AFFINIS, B r.]
Gen. Char. Perianthium simplex, membranaceum, urceolatum. Fructus, Capsula vel Utriculus monolocularis.
Gen. Char. Perianth simple, membranaceous, urc'eolate. Fruit, a Capsule or Utricule of one cell.
Radix e libra plerumque solitaria, simplicissimà, duas
ad très uncias longa, filiformi, infra prope basin
egrediente, apice calyptrata.
Frondes aggregatoe, natantes, duas ad quatuôr lineas
longæ, obovatæ, superne plante, minutissime
atque obscure reticulatæ, Vi ri des, subtus- heini-
sphoericoe, albidæ, vesiculoso-rëticulatæ, areolis
magnis convex is : basi angustiore ad marginem
. utrinque fissæ, rirna vel gemmifera vel florifefa.
Gemmæ cito ex plana tæ sunt in novas frondes, et
hæ frondes itaque proliféras.
Flos minutus, hermaphroditus, vix ultra rimam frondis
productifs.
Perianthium minutissimum, suburceolatum, eroso-
truncatum, membranaceum, pellucidum.
Stamina duo ad unum latus germinis inserta, vel solitaria.
Filamentum pistillo longius, album, valde
succulentum. Antheræ didymæ, lobis rotunda-
tis, flavis, verticaliter dehistentibus.
PlSTlLLUM : Germen subrotundum, obliquum, hinc pla-i
niusculum : Stylus perianthio longior, albus :
Stigma dilatatum, concayum.
Pericaupium subrotundum, ütriculatum, exsertum,
compressum, hinc planum, sæpe altero latere gib-o
bosum, apice emarginatum, stylo brevi termina-
lum, mono-tetraspermum.
Semina transversim posita, ad basin utriculi, vel.peri-
carpii eorum medio affixa, elliptica, striata, dorso
• præcipue.
Albumen copiosum, carnosum.
Embryo 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.
Fronds 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 convex: at the base ■
- narrower, and cleft on each; side at the margin;.
which cleft either bears, gemmas or flowers. The
gemmas are soon developed into new fronds, and
these fronds are again proliferous.
Flower minute,' hermaphrodite, scarcely produced
beyond’ the cleft of the frohd.
P e r ia n t h very small, somewhat pitcher-shaped, truncated
and erose, membranaceous and pellucid.
Stamens, either two, arising from one side of the germen,
or solitary: Filament longer than the pistil,
white, very succulent: Anthers didymous, with
the lobes rounded, yellow, opening vertically.
P i s t i l : Germen roundish, oblique, flattish on one
side: Style longer than the perianth, white:
Stigma dilated, concave.
Per ic a r p roundish, utricular,;, exserted, compressed,
plane on one side, often gibbous on the other, •
notched at the apex, and terminated with a short
style, one- or four-seeded."
Seeds transversely placed a t the base of the utricule
' or pericarp, affixed by their middle, elliptical,
striated, especially at the back.
Albumen copious, fleshy.
Embryo small, cleft at the apex almost into two coty-
ledons, Opposite the hilum: Radicule directed
towards the hilum.
%. ULemnagibba (nat.size). Fig. 2. Proliferous plant (magnified). Fig. 3. Flowering plant Fig.4. Single
frond, viewed from the underside. Fig. 5. Flower, the rima or cleft in the frond being laid open to show°it.
M . 6. Flower separated from the frond. Fig. 7. Perianth broken away to show a pistil and stamen. Fi*. 8.
Fructified plant. Fig. 9- Pericarp or Utricule. Fig. 10. Side view of ditto. Fig. 1 1 . Seeds. -Fig. 12. Sm<de
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. .
•vin thé*earlier part of this work I have had the satisfaction of figuring and describing the fructification o f two
species of this curious genus, and of bringing forward many particulars not before known to botanists. In the
month °t July of last year, my friend Dr. Greville sent me flowering specimens and a sketch o f the flowering
fr . s °*Lemnagibba ; and W. Wilson, Esq, of Warrington, communicated to me very perfect specimens in
• -ie*r his place of residence>in September of the same year: so that by the assistance of these two’
aoie ootamsts, it is my own fault if I do not give satisfactory details of this species also.
Ihe general character of the fructification and mode of growth of the fronds will be found to be similar to that
oi tne Lemna trisulca and L. minor. Here both Mr. Wilson and Dr. Greville observed, that,when two stamens
l i p # l ? | one. 'vas protruded at a time; which goes far to confirm an idea previously hinted at,— that each
. Jiff” * t0 oe considered as a separate flower acting independently of the other, and coming to perfection at
nerent period : the latter gentleman further observed, that each seed-vessel contained four seeds; whereas I
cam1- M P M S t ! one “ the former sPecies. Micheli, indeed, had found as many as six seeds* in each peri-
P, out he has represented them erect— and they often appear erect, through the semi-pellucid covering: but a
leiioU esa™Inatl.0lil "'ill show that in every instance the natural position of the seed is transverse with regard to its
Mtv r i-at U-is fixecl by tbe middle on the underside to the bottom of the seed-vessel; and they are‘only forced
than •1!'ect,on by tbe smallness of the pericarp and the enlargement of the seeds (whenever thei'e is more
even t E J WS-theSe- lat,ter an .alt.ered Position : but attachment is still the same, the raphis is stretched, and
The spprU h Penfai p ls altered in lts for®, becoming gibbous; and its point of attachment as it were, excentral,
a to n eM BW SH a‘e very deepl-Y striated> and the raPhis communicates most distinctly with a brown tubercle
where thl ’ * . brown tubercle is a portion of the inner lining of the integument, as may be seen at fig. 12
copious » T H ° l the inJteg.uJmf nt is cut away> but the tubercle is not thereby removed. The albumen is
iX . ’and tb® embryo has so decided a cleft; that it might without any misapplication of term be called dicoty-
a ciett has been seen in the embryo of this or some other ledonous, species o f the genus by Mr. Brown and
Mr. Lindley: and tïië°fcr r acute observer has noticed its existence in the genus Aru more lsi°“lld 8°“Ul’g “P™ 1118 sul* ce of pools and ditches, I believe, throughout Britain, but is much
to nossp«. ,i " “ an 111 Scotland. The Lemua generally are considered, like the fresh-water Conferva:,
pro,Per‘J °.f ponfyiog the unwholesome air in marshy places, absorbing this air during the day, and
'gen during the night.
surmounted by bracteæ, r