in greenboiises and hotliouses, •warm springs, outlets of warm
water from steam engines, brackisli ditches, all these have their
own peculiar forms, and experience will soon prove th at where
the favourable condition of quiet humidity is found, search will
seldom be in vain. Of course, during exceptionally dry
weather localities which would otherwise give satisfaction may
produce nothing but disappointment.
The methods of collecting do not much differ from those
adopted for other kinds of pond life. A japanned case with
from six to twelve corked te s t tubes will usually suffice for a
day’s collecting. Filamentous AlgK, such as Spirogyra, Clado-
plwra, &c., may be wrapped singly in paper, and a number of
these packets can be contained in a small tin box. I t is always
essential to keep each “ gathering ” by itself.
Preservation for future study, or for the herbarium, will be
secured by the usual methods of floating and mounting marine
Alg», first cleansing the specimens by well washing in a flat
dish or soup-plate, and finally passing under them a slip of
clean white paper, which is raised so as to take up th e Algie in
the middle, well floated into position, draining off the water,
and then drying, with th e least pressure possible. For minute
species, and small specimens, th in flakes of mica are preferable
to paper, for many reasons, especially th at they can be placed at
any time under the microscope and examined. The Falinel-
lacece, and similar groups, will be of very little service if dried
in any other way. Most species will adhere of themselves to
either paper or mica, the exceptions, such as Vaucheria and some
Cladophorce, can be fixed with gum tragacanth.
Some difficulty may probably be experienced in mounting
satisfactorily specimens for the microscope. We have seen
“ slides ” in which the specimens were still green and life-like
after having been mounted for twelve years in the water in
which they were collected, but unfortunately there is always a
risk of leakage with mounts in fluid, I f the medium is denser
than the contents of the Algse cells, the endochrome will be
contracted and the walls collapse. One objection to mounting
in glycerine, or glycerine and water, is the density of the
medium, and consequent collapse of the cells ; another, th a t in
time, use what precaution you may, the cells will leak, more or
less, in the majority of instances. No medium has yet given
us absolute satisfaction, but all things being considered, we are
most favourably disposed towards glycerine jelly, which is too
dense to enter the cells, and does not alter the form more than
glycerine would do. We may add th a t the slides should always
lie fla t in the cabinet, and not on edge, and they should not be
left exposed to the light, or the green colour will soon be lost.
Hints for cultivating in growing cells, or preservation in
small aquaria, are scarcely necessary in these days of manipulation.
Many forms of growing slides have been designed
and described, each possessing some special advantage, and
arrangements of common glass tumblers, communicating with
each other by small syphons, or lax threads, will keep up a
constant flow of water, sufficient to preserve Algæ living and
thriving throughout the year. The life-history, changes, and
development of many species still require to be patiently investigated,
and for this purpose there are ample contrivances, all
that is required being leisure, patience, and perseverance.
I t can scarcely be necessary to insist on the presence of fructification,
if a given species is to be accurately determined. This
is especially the case in OEdogoniaceæ and Zygnemaceæ, but it
applies also in a less degree to the majority of families. The
great difficulty that is experienced in determining, with any
approximation to accuracy, many of the species described by
authors half a century ago, lies in the insufficiency of the characters
of the fructification. A large number of species of
OEdogonium, for instance, as recent as Hassall’s work, cannot be
definitely placed on account of th is insufficiency. This may at
the same time serve as a caution to the inexperienced, th a t it
will be worse than useless attempting to affix a name to specimens
collected in a young or imperfect condition, at any rate in
genera the fructification of which is known, and embodied in
th e generic and specific characters.
Although it can hardly be considered essential to allude in
this place to theories which have been propounded in connection
with Fre sh -W ate r Algæ, we may make a passing allusion to
the suggestion th at sexually distinct filaments exist in the