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diflerent textm-es. aU, however, very gelatinous, aud modifications of the three layers forming the leaf, there arc
1st the su p rfc ia l tissue (or cortex) consisting of small ceUs, closely packed and full of chromule, gradually opening
cut into 2nd. an intermediate tissue of mnch larger cells more loosely placed, with little or no contained ehromulc
separated by much gelatine ; and 3rd, an eUiptical core placed in the long axis of the petiolo, composed of stUl smaller
ceUs, separated by broader masses of gelatine, wbicb latter is permeated by canals, fidl, as are tbe smaU ceUs of
chromule. ’
2. Each ramulus, from which proceed tbe two petioles, wbose stnietme we have just described, presents no vciw
.mportan difference from them; tbe core no longer stretches across it, however, but the whole petiole within the
superficial portion is augmented by a newly developed tbougl, iucUstinct zone of ceUuLai- tissue, thus deposited between
the superteial (or cortical) aud intermediate tissue. At tbis period tbe cortex is somewhat broader, and tbe
mtormediate tissue has become, througli the absorption of tbe gelatme, much more conspienons; tbe ceUs being
larger and the spaces between them naiTower; Uttle or no change is perceptible iu tbe core itself,
3. The branch is very materiaUy different from either of the above, for wbat was bitberto the petiole is now
enclosed (aU but its cortex) m a very broad zone of ceUular tissue, wbose ceUs ai-e large and thin towards tbe
old tissue elongated and of a different shape, so as to show the Une of separation between tbe two periods
of g iw th (see B of the plate Lessonia).
From tins time forward tbe normal mode of growth Mowed by the stem exhibits an additional layer or
zone of ceUular tissue for every subdivisoii of tbe frond, (shown at r t 1, wbere six are mterposed between
the cortex and core). It is not probable, however, tbat tbis numerical relation can be always evident, or that
the number of subdirisions of tbe frond wUl indicate tbe rings of growth in a large stem, Tbis uncertainty
arises from tbe branches bemg frequently broken off; added to wbicb. tbe growth of tbe sea-weed is veiy rapid
and there bemg no period of rest, irregnlar zones may be expected, or their absence from tbose branches of tbe plant
whose leaves are mjurecl.
In then- anatomy the stems of L.fuscescem aud L. nigrescens do not differ much from tbat of this species
except that the air-ceUs are copious in tbe stems of tbe former, and much rarer in the latter; in whicb also
the cortical substance is much broader.
In the elegant lessonia Sindairi, Harv. MSS„ from California, the stipes (wbicb bears but a solitary Uiiear
frond) IS terete, and m the specimen we examined, contains a central core, reaching Iialf-way across tbe diameter
There are apparently two rings of tissue beneath tbe cortex, separated by a zone of very large eeUs (air-eeUs°):
wbenre it is d ^ e u lt to account for tbe stem being terete, for the frond is plane, and tbe core three times longm
than broad. Nor is it easy to explain the origin of the two zones snrronnding tbe core; if they reaUy be sueecs-
sively deposited, it is possible that the frond is turn years old; if not, tbat the large ceUs are air-eeUs and do not
indicate a hne of separation between two successive deposits.
^ I have stated tbe growth of the Lessonia to be veiy rapid; this is proved by tbe zones of a five-ringed stem
bemg progressively broader towards the eircumference, Tbe probability, too. of one being added for every time tbe
lammm iiudiq and the fact that the process of subdivision is continued in geometrical progression, all L o u r tbe
opinion that these Algm attain then- enormous bulk iu a very few months. Tbe vast masses washed up on the outer
S rd e trpm tn t
The an a lo g between the mode of growth exhibited by tbis genns and an Exogenous tree, is. though incomplete
very obvious; both increase by layers deposited outside one another, within a cortical substance, and botli con’
tain an axis of tissue different from tbat forming the greater part of the tru n k : here, however there nre no
traces of medullary rays. We conclude this subject witb tbe observation, that tbe periodical increment of the
runk being dependent on. or coincident with, the formation of the laminm. tbese appear to perform the offieo of the
loaves m the higher order of plants ; and tbat the Lessonia is also in this respect analogous to an Exogenous plant
FaUdands, etc?) FLO RA ANTARCTICA. 4C1
deprived of its woody tissue, for it is a stem composed o f layer upon layer of cellular tissue, deposited round an axis,
wliicli, like tlie pith, when once formed, is afterwards but slightly modified.
P late CLXVII.—CLXVIII. B. apex of branch and frond of the natui-al size; B 1, transverse section of young
stem : —magnified.
4. MACROCYSTIS, Ag.
1, MAnn.nnYSTTsp yrifera , Agardli, Bp. Alg. vol. i. p. 4 7 . Nov. Act. N a t. Cur. vol. xix. p. 297. t. 26
f. 2. Post, et Ruppr. Illu st. Alg. p. 9. t. 6 ; et p. 4. t. 39. f. 22, 23. PI. Antarct. P t. 1. p. 178. M. communis,
Bory, in B ic t. Class, v. x. p. 8. M. planicaulis, Agardh in Nov. Act. N a t. Cur. I. c. Lessonia ciliata.
Post, et Ruppr. I, c. (young state).
Var. |3. in teg rfro n s; foliis fere integerrimis planis rugoso-plicatisve. M. iiitegrifrons, Bory, I. c. t. 6.
Var. y. angustfrons ; vesiculormn parietibus tenuibus, foliis u t in M .p y r ife ra . M. angustifrons, Bory,
l . c . t . 8 . Agardh, 1. c. t. 28. f.4! and S. Post, et Ruppr. t .b .
Var. Ô. zosterafolia; folüs anguste lineari-elongatis planis. M. zosteræfolia, Bory, ^ c .
Var. €. luxurians; folüs 3-8-pedalibus 8 unc. latis basi cordatis membranaceis plicatis margine longe
ciliato-dentatis, vesiculis late obovatis parietibus temübus, caule gracili. (Tab. C LX IX .—CLXX.)
Var. C membranacea ; foliis u t in i f . p y r ife ra sed tenuissüne membranaceis planis, vesiculis parvis
cUiptico-ovatis utrinque subacutis.
Var. T). HumboldtU ; foliis lineari-elongatis planiusculis, vesiculis globosis tenuibus. M. Ilumboldtii,
auct. M. pomífera, Bory.
H a b . Throughout th e A ntarctic seas, between the parallels of 40° and 64°, both attached, and floating
over th e whole ocean.
-After a very attentive exanünation of many himcheds of specimens, we have arrived at the conclusion that all
the described species of this genus which have come under our notice may safely be refereed to Macrocystis
pyrifera. Nor can these variations excite surprize, when it is considered that this gigantic weed is subject to everj*
ricissitudc of chmate, of temperature, and exposure ; that it hterally ranges from the Antarctic to the Arctic circle,
through 120 degi*ees of latitude ; that it lives and flourishes, whether floating or attached, gi-owing in bays, harbours,
or the open sea when most distant from land ; and, lastly, that it equally adapts itself to the calmest or most
tempestuous situations, to waters of uniform depths or those which rise and sink with the tide, to dead water or to
strong cm-rents. One thmg alone it reqim-es, and that is, a mean depth of six or more fathoms ; for, like the Lamina-
rioe of our own shores, it, and others of the same tribe in the south, iuvai-iably form the outer belt of marine vegetation.
A few remarks upon the above varieties may be interesting ; shoniug how much their characters depend upon
natiu-al causes, and how much more upon mutilations of the specimens, or changes during the operation of di-ying.
Variety j3. integrifrons. This we have received from various parts of the west coast of South America ; its
characters rest almost entfrely on the want of ciliation at the mai-giu of the frond, wlüch is much dependent upon the
portion of the plant from which the specimen is taken, the lower leaves being always nearly entfr-e; also ou the
state of the waters, those plants which gi-ow in quiet bays having very much developed cüiæ, whilst those from the
main ocean or stormy coasts arc generally more entire.
Variety Ô. is a plane and narrow-leaved state of üf.jT/ri/b-® ; we have traced aU the changes in
one specimen of M.pyrifera, from vety rugose to perfectly plane. Young specimens and terminal leaves are generally
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