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ness, and then by a moderate fresh supply to produce a
continued change of the watery element. Eor the same
reason, and to prevent the souring of the soil, which always
takes place more or less when it is in contact with stagnant
water, an outlet at the bottom of the case should be carefully
provided, by which all the free water at least, which
drains through after the soil has been irrigated, may be
removed as it accumulates.
As to aspect, the northern is decidedly the best, principally
for the reason, that in such a situation the sun has
less influence on the temperature of the interior of the
case; and extremes of confined heat would be anything but
favourable to these plants.
The appearance of the case would, no doubt, he improved
by covering the soil entirely with living green Sphagnum
moss, which, if neatly packed on the surface with the. tops
of its stems uppermost, would continue to grow and retain
its verdure. Most of the species of Club-moss would prefer
to grow amongst the Sphagnum, which, as it made fresh
growth, should, to prevent its being drawn up and smothering
the plants, be neatly clipped down occasionally with a
pair of scissors.
The interest of such a collection, so far as their appearance
is concerned, would depend of course upon the taste
with which the rock-work was designed and executed, and
the plants distributed about i t ; but whatever the result as
a matter of taste, the study of the living plant might be
prosecuted without inconvenience, and—which could never
happen in their wild localities—all the species might be
brought under the eye at one time, for the purpose of contrasting
them, and studying their differences.