THE COTTAGE' GARDENER AND COUNTRY GENTLEMAN, May 11, 1858. 
become toO large, they lose much of their beauty. I shall 
speak cf them more fully on another occasion. 
The botanicallv-inclined visitor to Berlin should not fail to 
get a sight of another garden—that of Herr Decker, the prin¬ 
cipal printer and publisher of the city. It is a kind of private 
nursery, for he receives the seeds and plants collected by a 
German traveller (Dr. Kars ton), in tropical America, and 
raises them for sale. From these importations are many rare 
plants, particularly in the way of Palms. Among them is 
Chamcedorea graminifolia , the most elegant of all the family, 
its long narrow-pinnate leaves and drooping flower-stems ren¬ 
dering it well worthy of a place among the most select of 
foliage plants. Then there is the very rare and beautiful small- 
fruited Ivory-nut Palm ( Phytelephas microcarpa), DecTceria 
Corneto, one of the tallest trees known ; various species of 
Kloptockia, GEnocarpus, &c.: indeed, the houses are perfectly 
crowded with rare plants. One greenhouse looked very gay 
in summer with the orange-scarlet Tropceolum tricolor , the 
yellow T. brachycercis , and the blue T. ccerulea , hanging in 
festoons from the rafters ; while the stages were covered with 
different varieties of Achimenes, Gloxinias, Gesneras, Oxalis 
Bowel , and O.Jloribunda , all flowering freely. 
Some of your correspondents have, I see, been detailing the 
results of the excessively hot summer we had last year. The 
most singular thing here was that it caused several old plants 
of JDasylirion acrotricheum to flower. This has been culti¬ 
vated for many years, but was never known to bloom before ; 
while last summer I heard of no fewer than ten plants throw¬ 
ing up their flower-spikes ; all were, I believe, male plants. 
This Dasylirion throws out from the top of a short stem a 
mass of long narrow leaves, which droop gracefully all round; 
from the centre rises the flower-stem, from ten to eighteen feet 
high: this grows very rapidly; one, which I measured, as 
much as nine inches in the twenty-four hours. The upper 
portion was covered with inconspicuous, catkin-like clusters of 
male flowers. It is a Mexican plant.— Karl. 
THE FRESH WATER AQUARIUM. 
-G.WHYMPSR.Srr' 
A fresh water aquarium is now within the reach of high 
or low, rich or poor; and a more beautiful ornament for the 
sitting-room, blending recreation with instruction, has never 
yet been brought into public notice. 
During the last two winters the writer has been entirely 
confined to the house ; so, unable to enjoy the variety of ex¬ 
ternal nature, the world of the aquavivarium became its sub¬ 
stitute. Observations on the manners and customs of its in¬ 
habitants, the beauty of its evergreen vegetation, its changing 
scenery, and its microscopic wonders, have presented attrac- 
i tions which seem still as inexhaustible as ever, constituting ! 
87 
powerful witnesses of the Divinity of their Maker. And all 
this with the minimum of attention an invalid can bestow; j 
for the balance of vegetable and animal life being never : 
interrupted, the water remained pure and bright from the j 
j first. 
If we take a jar of water and place therein a fish, we shall ' 
find that, ere long, it will come to the surface gasping and 
panting ; if still left to itself, suffocation would soon put an 
end to its existence. Such is the fate of the many hundreds 
of sticklebacks yearly caught by juvenile anglers. They are 
carried home in triumph, two days afterwards their carcases 
are thrown on the ash-heap, or found floating amid prismatic 
films on the surface of the water-butt. But the lives of the 
fish might have been preserved had our juvenile friend taken 
home but three specimens; placing a sprig or two of the 
common pond Star Weed (Callitriche) in his bottle. The 
, existence of his captives would have been prolonged, and the 
pleasure of their youthful owner enhanced, as every other day 
lie dropped in a few crumbs of hard biscuit, or a tiny w T orm, 
and enjoyed the scramble which was sure to follow. 
This principle of mutual accommodation was carried into 
practice by Dr. Lankaster, in 1849, and explained to the 
Chemist’s Society, by Mr. Warrington, in 1850. 
When placed in the direct rays of the sun, any growing 
water plant will be soon found covered with minute bubbles, 
i which will eventually be seen rising in rows to the surface, 
j Now, these globules consist of pure oxyg-en —the vital air so 
necessary to the existence of the animal creation. Without a 
proper proportion of oxygen, we should languish and die ; 
but God has wisely ordered it, that vegetable life should 
provide this valuable gas, at the same time seizing on noxious 
vapours, and transforming them into green tissue and leaf, j 
So in the world of water, the poisonous carbonic acid given 
off by fishes and insects is taken up by the wnter plants, and I 
converted by them mto waving bannerets, or delicately- 
feathered foliage, which, in their turn, are continually fur¬ 
nishing the air of vitality to their benefactors. With this 
mutual assistance, the aquarium would alone be self-support¬ 
ing ; but further provision has been prepared as an extra 
support to this natural circle. 
The misroscope has lately brought under notice a species 
of minute locomotive plants which (like the new sect of 
Angelites) eat nothing at all, but live on carbonic acid and 
ammonia absorbed from the water. Being continually on the 
move, they are most valuable assistants for extracting foul 
gases. Wherever they go, they can never be said to make a 
useless journey. 
The water snail ( Planorbis corneus ), too, must not be for¬ 
gotten, for he is one of the chief officers of our Board of 
Health. He is too vigilant to suffer any decaying matter to 
remain long in one particular place, and is to be seen almost 
always active, mowing off unnecessary eonfervoid growths, or 
clearing away nuisances in a style certain “ Boards of Talk ” 
would do well to imitate. 
Here, then, is the rationale of the fresh water tank. 
The fish gives off carbonic acid. This carbonic acid is taken 
up by the plants, which appropriate the carbon, and give off 
oxygen, which the fish consume. 
In stocking our aquary, then, we must always provide a 
supply of oxygen more than adequate to the wants of the fish 
to be introduced, sufficient vegetation to absorb all foul gases, 
and to keep the water pure and clear. 
After long observation, the writer finds the following pro- 
1 portions of vegetable and animal life the most desirable for 
the production of a self-sustaining parlour collection. 
For each gallon of water—two healthy plants, and three ! 
fish (no specimen to exceed two inches and a half in length ). 
The great mistake of the present day is, to cram large and 
unwieldly creatures into aquaria of but moderate dimensions ; 
consequently, they look miserably unnatural, and, consuming 
as they do, a large quantity of oxygen, a periodical renewing 
of the water is necessitated. Small fish, on the contrary, are 
lively in their movements, and far more interesting. Soon 
they make themselves quite at home, and show by their 
gambols and fishly antics that they are happy and comfort¬ 
able. In my next I shall (d.v.) notice the construction of 
fresh water tanks.—E. A. Copland. 
