AQUATIC PLANTS. 



27 



the centre, and from eighteen inches to two feet deep 

 at the sides. A temperature of 85° must be main- 

 tained, and one foot of four-inch piping- to twelve 

 cubic feet of water is found to secure this. For 

 Nyn>i3hasas, another tank should be provided, with a 

 temperature of 70° to 75°. The Victoria may be 

 regarded as a luxury, but these are much less, costly, 

 as the best may be grown in a smaller tank with 

 less heat. Whether for the Victoria, or for Nym- 

 phaeas and a general collection, there is no better 

 arrangement than that of the Water-lily House at 

 Kew. There is a large central round basin — ■ 

 generally the best shape — with a margin but little 

 raised above the level of the floor, so that the plants 

 are seen to the best advantage, and from this princi- 

 pal basin there is communication, beneath the circu- 

 lar path, with corner tanks, for the culture of 

 Nelumbiums, and plants that grow in shallow water 

 or mud. This house is square, and as these corner 

 tanks serve a valuable purpose, there is probably no 

 better shape. Nymphysas are always grown in pots 

 or tubs, and it is important to observe that space 

 may be economised by keeping the crowns near the 

 surface of the water, as the leaves spread less than 

 they would do when rising from a depth. The 

 depth adopted at Oxford, where for many years 

 they have been a speciality, is about six inches. In 

 designing a house, provision should be made for 

 planting out the Nelumbiums, and of course the 

 Victoria must be planted out as hereafter described, 

 but all other kinds may be sufficiently developed in 

 pots or tubs. With the Victoria, a few Nymphaeas 

 and some other plants may be cultivated, but 

 the Victoria must on no account be crowded by 

 them. Some kinds, such as Vallisneria, Eichornia 

 (Pontederia), Limnocharis and Pistia, may properly 

 occupy the outside spaces in order to fully occupy 

 and dress the tank. Aqiiatic plants almost invari- 

 ably require the fullest amount of light, and they 

 should not be overshadowed by the foliage of Palms 

 or other specimens. 



The requirements just referred to are somewhat 

 extensive, and not always possible, but many kinds 

 may be grown in tubs and even large pots, which 

 cost little. Parafiin casks cut in two, each part 

 forming a tub, answer well. Before being used, the 

 inside should be charred slightly with a burning 

 wisp of straw, in order to burn out the oil. These 

 tubs have been used successfully in the Cambridge 

 Botanic Grarden for Nymphcea flava, N. ctjanea, .N. 

 scutifolia^ N. pygmcea, N. Devoniensis, Nelumbiuin 

 luteum, and Sagittaria montevidensis, though, as the 

 water is not heated, there are others that will not 

 succeed. Nymphcea gigantea, apparently for want 

 of more heat, refuses to start, but the difficulty 

 might bo obviated perhaps by standing the tubs on 



flues or pipes, where that is possible. Some kinds, 

 as for instance the Ouvirandra, do much the best in 

 vessels of moderate size, as they are then more com- 

 pletely under control. For several kinds, large in- 

 verted bell-glasses answer admirably, and they 

 will stand easily on blocks of wood hollowed out. 

 Aponogeton distachyon makes a charming acquisition 

 for the green-house, if a strong tuber is planted 

 in a bell-glass with a little soil in the bottom. 



A natural arrangement for the culture of tropical 

 aquatics has not yet been attempted, though, no 

 doubt, success is possible. In a tank of irregular 

 outline, formed with stone as for rock-work, various 

 bays and lagoons might be arranged for particular 

 kinds ; indeed, with some thought, every one might 

 be provided with a special position suiting its re- 

 quirements. It is easy to imagine a very fine 

 effect, not only from, the aquatics, but also by the 

 introduction of a variety of plants that would grow 

 well in a moist atmosphere, for many of which rock- 

 work would be provided. Nepenthes, and various 

 Aroids, as Monstera and Philodendron, may be 

 mentioned by way of suggestion. All those plants 

 which are grown in pots or tubs, partly in water, 

 should be planted out, and there are many subjects 

 that would be especially ornamental. Such are Thalia 

 dealhata, Arundo mauritauica, Papyrus, and Acrosti- 

 chum auretim, the last of which grows in the West 

 Indies much as the Osmunda does in Britain. For 

 these, slopes clothed with Selaginella would perhajDS 

 be best, and about on the rock-work we should plant 

 Begonias, Pellionias, and a variety of small-growing, 

 choice kinds. 



There are several desirable aquatics that have 

 been lost, or yet remain to be introduced. Seeds, 

 generally, may be sent dry, but the precaution of 

 sending them also in small phials of water should 

 be adopted when they are probably important. 

 Barclaya is the only genus of JSfymphceacem that has 

 never been cultivated in this country. There are 

 two species native of Malayan waters, which, if not 

 highly ornamental, are of sufficient interest to be 

 sought for. We do not now grow such interesting- 

 kinds as Cahomba aquatica and Desmanthus natans, 

 the charming Heteranthera limosa is seldom seen, 

 while we have also lost Ouvirandra Bernieriana. 



The following is a selection of the best kinds in 

 cultivation. 



Azolla caroUniana. — An extremely charming and 

 diminutive floating plant, which suggests a setting 

 of tiny jewels in imitation of a bit of some small 

 Selaginella. It rapidly increases by division, and 

 spreads over a large space ; it is emerald-green in 

 colour, or tinted brown if exposed to sunshine. In 

 summer it flourishes out of doors, and at Pinner a 

 large pond was covered by it; but it has been 



