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10 ON LEMNACE.E AND THE RAPHIDIAN CHARACTER.
Waterfowl and AVater-Voles ;
and I have elsewhere described the boun-
tiful provision of its starch and calcareous raphides for a suitable ad-
junct to the food of groAving animals. Indeed, to me, a Duckweed-
patch always appears delightful from its very utility, both in this way
and as a procreant cradle of those beautiful and mysterious organisms
which live and move and have their being on the boundaries of the
two great kingdoms of organized nature. In short, a Duckweed-patch
is not only the home of many happy famdies, full of life and enjoyment,
but it provides either nutriment or shelter, in one shape or other, to
many creations, from Mammalia down to the Protozoa and Protophyta ;
and is truly a prolific and provident field, with a little world of its own,
emineiTtly valuable and useful, although its complete history yet re-
mains unwritten.
Lemna trisulca.—The late Dr. Lindley and other eminent botanists
denied that there is an epidermis on plants which live habitually under
water. "Whether this Lemna be always thus totally immersed might
a(bnit of question, though it is fairly described, in ' English Botany,'
as having its " fronds submerged." In the same great work we find
oidy this plant under Staurofjeion, a section of which one of the cha-
racters there given is "epidermis absent ;" and this, no doubt, accord-
ing to the common view, which nevertheless needs further inquiry.
I have often found an epidermis on parts of plants which are ahvays
covered by water ; so, it would seem, have other botanists, for Schnetz-
ler, in his memoir on Utricularia, remarks that " in entirely sub-
merged aquatic plants the leaves are destitute of stomatn, and absorp-
tion and exhalation take place through the whole surface of the epi-
blema." But now we are only concerned with Leimiacece, on both
sides of the fronds of which an epidermis is commonly present, as may
be well seen in L. minor. And L. irimlca is thus invested with a
distinct but very delicate and transparent epidermis, which resembles
the same tissue on the other species of the genus, but wanting the
storaata which belong to their upper surface.* The margins of the
* Whilst these sheets arc in the i)rcss, our attention has been directed to
JJr. ncKelmnicr's recently-published monograpli ' Die Lemnaceen,' which contains
full descriptions and numerous figures of the structure of all the species
of tl.e Order lemnat-e^. On tab. vi. fig. 8, the epidermis of an aerial frond
^ufUproxs) of L. trisulca is figured with a stomate. The term epidermis is,
by some botanists, restricted to- its perfect condition when provided with sto-
mata, the thin membrane covering subterranean and subaciueous organs beinotermed
epiblcma
"
or epithelium.—Ed. Jouen. of Box.