AQUARIUM. 



711 



much light as possible is admitted to the plants, 

 the bottom and surface temperature kept both at 

 80° to 85°, allowing a rise of several degrees in the 

 latter during sunshine. The night temperature is 

 6° less. A constant supply of fresh soft water is 

 admitted by a half-inch pipe, and the overflow 

 escapes at the opposite corner, and is conveyed 

 to a tank in the adjoining house. As the leaves 

 begin to decay, they are cut off, to make way for 

 the young ones, one of which generally presents 

 itself every second or third day. The Victoria 

 Eegia is a perennial plant in its own country, and 

 so it has proved itself to be in some collections 

 in Britain, as at Kew, Sion House, &c. In the 

 former establishment we observed it in flower 

 during its third year's existence. With us, how- 

 ever, it has proved, for three successive years, 

 no better than an annual, dying always towards 

 autuum, but producing abundance of seed : one 

 capsule this year contained 268 seeds. We grow 

 it, therefore, annually, but find great difficulty 

 in getting the young plants along, particularly 

 early in the spring. The cloudy atmosphere and 

 long absence of sunshine may be the cause of 

 this, as well as its not surviving the winter. 

 Almost similar difflculties have occurred at 

 Dalvey, the only other place, we believe, in Scot- 

 land where it has flowered. 



The Nymphwas are propagated by seed, and 

 also by division of the roots. Some of them 

 seed so freely, and vegetate in the bottom of 

 the tank, that they require to be often weeded 

 out. As they are much smaller-growing plants 

 than the foregoing, we usually plant them in 

 pans from 12 to 18 inches in diameter, and from 

 6 to 12 inches deep, and submerge them round 

 the edges of the outer tank. When their season 

 of growth is past, the roots are taken out and 

 placed during winter in smaller ones, the soil of 

 which is kept only moderately damp, and placed 

 in a temperature of from 50° to 55°. This con- 

 stitutes their season of rest. They are re-potted 

 again in spring, and treated as above. 



Zimnocharis and Pontederia are of easy 

 growth, propagating freely by extension, but 

 succeeding better in a much less heat, say from 

 57° to 65°. 



Papyrus, one of the species of which was a 

 plant of great importance to the ancient Egyp- 

 tians, furnishing, as it did, a material for writing 

 upon before the invention of paper, is also of 

 easy culture, not requiring much bottom-heat, 

 and succeeding well if planted in a large pot set 

 in a tub of water. 



Pistia floats about on the surface of our 

 Victoria tank in great abundance; is difficult 

 to transport, unless sent in a jar of water. 

 It winters best when its roots are in soil, 

 • and plunged in a warm tank ; dming sum- 

 mer it luxuriates floating on the surface of the 

 water. 



Vallisneria is a genus of no particular beauty, 

 but sufficiently interesting in a botanical point 

 of view, being generally selected by the micro- 

 Bcopist for the exhibition of the circulation of 

 the sap in plants. The leaves, which resemble 

 the leaves of some long-leaved grasses, evolve a 

 continued stream of oxygen gas, which rises in 

 a current of minute bubbles, and particularly 



BO from parts that may have received slight 

 injury. 



The other tropical aquatics we have named 

 are all of the easiest culture, and are readily 

 propagated by subdivision. 



Soil. — Contrary to the majority of other 

 plants, aquatics do not require a soil fertile 

 in vegetable matter, at least in a recent state. 

 Their natural soil is the bottom of lakes, rivers, 

 or ditches, composed of alluvial deposit to a con- 

 siderable depth, although sometimes a gravelly 

 soil. We find a fine rich aUuvial soil, formed 

 during ages along the banks of the North Esk, 

 free from stones or the roots of other plants, to 

 answer exceedingly well, and without previous 

 preparation or addition. The soil we refer to is 

 free of mineral ingredients likely to be injurious 

 to the roots. When the plants are finally 

 planted, about an inch of fine silvery sand is 

 laid over the surface of the soil in the case of 

 large plants, while small white pebble-stones 

 are placed over that in which the smaller are 

 set, merely to give the whole a cleaner and 

 neater appearance. 



Water. — It is important that the water be 

 pure and not charged with mineral matter. 

 Rain water being the best, we always use it ; 

 it being brought from a collecting cistern in a 

 leaden pipe, which is made to pass round the 

 boiler before discharging itself into the tank, to 

 avoid decreasing the temperature of the latter. 

 It is also necessary that it be kept clean and 

 fresh, and free of green slimy or mucous 

 matter, probably the first stages of various 

 species of Confervae, &c. This may be partially 

 kept down by skimming the surface of the water 

 daily, and in addition to this a few water-snails. 

 Limnsea stagnalis, if introduced, will breed, and, 

 as they feed upon such matter, render the water 

 clear and wholesome. It is possible, also, that 

 gold and silver fish assist in this nice operation 

 — at all events, we know that they devour the 

 numerous hosts of aphides which prey upon the 

 under surface of the leaves of the Victoria, 

 which, until we employed them last year, had 

 nearly devoured the leaves before they were 

 half formed. We believe that there are two 

 species of aphides attacking the Victoria : the 

 one we have referred to, which is an aquatic 

 species, or else capable of adapting itself to 

 a watery element, as it lives on the under 

 side of the foliage ; and another, which preys 

 on the upper surface of the leaves, is equally 

 destructive. By their united efforts holes are 

 often eaten quite through the leaves from half 

 an inch to an inch in diameter. Fumigation, 

 both of tobacco and Cayenne pepper, was tried 

 in vain, and no means we used had any effect on 

 the enemy till the introduction of the gold and 

 silver fish. The fish also perform other im- 

 portant offices connected with the growth of the 

 plant. An interesting paper, communicated to 

 the Chemical Society by Mr Warrington, seems 

 to establish this fact. " The fish," he says, " in 

 its respiration, consumes the oxygen held in 

 solution by the water as atmospheric air, fur- 

 nishes carbonic acid, feeds on the insects, and 

 excretes material well adapted for rich food to 

 the plant, and well fitted for its luxuriant 



