Journal of Proceedings.
xlix
"From the platform in front of the Grotto, the point which gives you
the finest views of the lake and rich woods, I gathered a bunch of the
Lemna which covers the water, and took it home, partly in the hope of
finding it in flower and partly to examine the Diatomaceae and minute
life among its tangled threads. I found the older rootlets covered with
Cocconeis placentula, but no flower of the duckweed; however, I placed
the plant in a saucer of water, and ou looking over it on Thursday had
the great pleasure of finding Lemna gibba in bloom.
"Boswell-Syme, in the last edition of Sowerby's 'English Botany,'
speaks of his never having discovered the flower in this species; and, as
it is the rarest of the Lemna, I have some hope that its occurrence in our
neighbourhood in bloom may not be uninteresting to the botanical
members of the Club, and that many others may share my enjoyment by
procuring specimens for themselves."
Mr. Lister's two 'notes' were illustrated by specimens and some
beautiful coloured drawings of the plants referred to in all stages,
executed by Miss Lister and himself. A cordial vote of thanks was
accorded to him for his communications.
Mr. C. Thomas, F.R.M.S., exhibited and described a new form of
" Life-slide " for the microscope, a modification of the " Hardy Vivarium,"
enabling it to be readily applied to observation with high powers. The
following is a description of the apparatus, to illustrate which Mr.
Thomas has very kindly had the accompanying woodcuts engraved by
Ruffle :—
A new form of "Life-slide" ("Thomas's Vivarium").
This vivarium was devised for aiding the microscopical study with
all powers of the Infusoria or other minute life which exist so abundantly
in our ponds and ditches. Many "life-slides," " compressors," and other
appliances have been used for similar purposes, but, so far as we know,
none possess the advantages which are claimed for this contrivance.
(1) Being composed entirely of glass and elastic bands, it is simple and
inexpensive in construction ; (2) for the purpose of being thoroughly
cleaned after use it may be taken to pieces and put together again with
ease and without the risk of breakage ; (3) the object under examination
may be kept alive and in a healthy state for almost any length of time,
and (4) may be viewed under the highest powers that are in any case
necessary or suitable for thorough examination of the most minute
organisms.
The woodcuts, figs. 3 and 4, represent the vivarium of the full size
suitable for use with the large microscope-stands of Messrs. Powell and
Leland, Beck, or Boss; but, of course, it can be made of any dimensions
to suit the size of the stage of the microscope employed. It is composed
of two pieces of plate-glass, one of which has a circular hole in its centre
(No. 1) or a segment of a circle cut out of its side (No. 2). A segment of
an india-rubber ring is laid on the imperforated glass in the manner
shown in the cuts, on this is placed a piece of very thin microscopical
glass (or talc) of suitable size, then the perforated slide, the whole being
firmly held together by a pair of elastic rings. We thus have a cell the
upper side of which is thin enough to allow high powers to work through
it, and which will hold fluid without leakage. The thin glass is so
supported by the upper plate, with which it is in contact over the greater-
part of its surface, that there is practically no risk of breaking it in
d