F am. ITT. L EM A N E A i.
3. L EM A N IA Bory.
Char. Frond attached, coriaceous, ramose, and cellular. Outer
cells small, polygonal, and firmlg adherent ; interior
larger, more lax, sphoerical, and empty. Sporules mo-
niliform, fasciculate, naked, arising from the inner vesicles,
and occupying the interior o f the frond.
Lemania Bory, in Annales du Museum, vol. xii., also in
Diet, class, ix. 274. ; Agardh, In Act. Holm., 1814, t. 1.
species 1, 2. Nodularia Link, in Sclirad. Jour., 1809,
p. 9. ; Lyngb. t. 29. Gongycladon Link, in Hort.
Bliyslc. 6. ' Trichogonus Palis, in Jour. Bot., 1808,
p. 123. (excel, sp.) Vertehraria Kouss, in Desv. Jour.
Bot. i. 143. Apona Adans. 13. Polyspermm sp. Vauch.
t. 1. f. 3., t. 10. f. 1, 2. Conf. sp. Dillw. t. 29. ; E. B.
1763.
The genus Lemania, like some other genera of freshwater
Algæ, would appear to stand almost alone, exhibiting no
very exact relation with any other division of this tribe, and
the only plant to which it bears any definite resemblance
appears to be the Lnteromorpha intestinalis, and this only in
its ramose habit, and in the cellular structure of the frond,
the reproduction in Lemania, though simple, being wholly
different from that of Lnteromorpha.
Vaucher, in his description of his genus, Polysperma, of
which Conf. fluviatilis formed the type, has not erred far from
the truth, and his generic name might, with propriety,
have been retained ; the chief mistake which he committed,
was In associating with Conf. fluviatilis the Conferva glomerata,
a plant in every way dissimilar to the former.
The branches of the fronds of the Lemanioe, in their young
state, are cylindrical; soon, however, they are seen to. become
dilated at regular intervals. I f one of these dilatations
be pressed between the fingers, their contents will be forced
o u t: on examining which, with the microscope, the observer
will be astonished to perceive that it is made up of a number
of beaded and i)lant-likc bodies, which the inquirer would ho
inclined, at first sight, to regard as the siiecics in its young
state : this opinion, on further investigation, woidd be found
to he erroneous; for if these tufted bodies be watched, and
kept in water for some time, the heads of the filaments will
soon be perceived to separate from each other, and each ultimately
to become develojied into a young plant resembling
tha t from which the seed was derived. The sejiaration of
the sporules which compose the beaded threads likewise takes
place naturally within the frond, and it is by their devclope-
ment that the dilatations of the stems, already referred to,
are produced, and by which an apparent resemblance to the
Batrachosperms is imparted to the plants of this genus.
Frequently, if tliese dilatations be examined with a lens,
numerous filaments may be observed issuing from th em ;
these are what Vaucher terms the young polysperms produced
hy the germination of the sporules, which are still
within the frond, and which developement of them is ordained
to take place in all cases to such an extent as to
occasion the rupture of the dilatations, and consequent separation
of some of the cortical cells from each o th e r; thus,
apertures are created, through which the sporules may pass
out, a condition essential to the perpetuation of the species.
The force with which this developement operates may be
appreciated when the cartilaginous nature of the frond is
considered.
I t is only the middle and upper branches th a t arc so
torulose, the lower being almost plain and cylindrical; this
arising from the fact of the sporules having all escaped from
tliese, which arc the oldest portions of the plant.
Bory’s account of the structure of this genus appears
to contain some strange errors. “ The Lemania;,” he remarks,
“ are articulated Conferva;, whose contiguous joints are
united the one to the other by a solid interior filament, very
well represented hy Vaillant (Bot. Paris, pi. iv. fig. 5.) in
V :i