AQUATIC PLANTa 



AQUAVIVAKH'M. 



structure of their extremities approximate* more to that of purely 

 aquatic than of terrwtriol animals. Their leg* ire short, and inserted, 

 or a* it were buried, ill the common integument* of the body, as far 

 M the elbows and knee* respectively, leaving apparent ouly a short 

 fln-liko paw, which is unadaptod to terrestrial progression, exactly 

 in proportion to its fitness as an organ of swimming. Their progress 

 on land is consequently slow and difficult ; they creep rather than 

 walk, dragging the body along the ground, and leaving a brood mark 

 behind them. Few species possess even this limited power of terrestrial 

 motion ; those which do however have the structure of the extremities 

 a little less approximated to the form of fins than the purely oceanic 

 species. The seals and walruses, for instance, have the bones <t i he 

 paws and feet similar to those of ordinary land-quadrupeds, only 

 much shorter and more flattened, and the hind legs are thrown 

 backwards in the same direction aa the tail Still they are enabled 

 to use the extremities in a certain degree for walking or creeping 

 n dry liuid ; but the numerous tribes of cetaceous animals, which can 

 execute no kind of motion whatever out of the water, have the bones 

 of the anterior extremities flattened and connected together like the 

 stones of a mosaic pavement, whilst the posterior members are entirely 

 wanting. The same is the case with the sea-tortoises, or, as they are 

 more properly called, turtles, when compared with those which 

 frequent fresh-water ponds and rivers ; the form of their extremities 

 approximates more nearly to that of fins than of feet, and their 

 aquatic habits constantly predominate over their terrestrial 



Thus it is that the peculiar form of the extremities not only 

 indicates the degree in which an animal is aquatic, but oven the 

 nature of the element which it frequents. If it inhabits fresh-water 

 ponds and rivers, its feet are simply webbed between the toes, but in 

 other respects perfectly developed, and its terrestrial habits predominate 

 over its aquatic ; if, on the contrary, it inhabits the salt water, its 

 feet are flattened into the form of fins, the hind legs are thrown 

 backwards into the plane of the body, and the aquatic habits greatly 

 predominate over the terrestrial. The first are, properly speaking, 

 wtb-footrd, the second fin-footed. 



AQUATIC PLANTS, or WATER PLANTS, are those plants 

 which live entirely in water, or which require a preponderating quantity 

 of water as the medium of their existence. The families of plants, like 

 the families of animals that live in the water, are found to belong to 

 all classes into which the whole have been divided, although those 

 belonging to the lower classes are by far the most prevalent. Many 

 of the families of plants having the highest organisation have members 

 belonging to them which are inhabitants of the water : of this the 

 JinHuncuim oquotilit is an example in the natural order Banunculacete. 

 All the species of the orders Nymphcuaeat, Callitricltaceff, Cerato- 

 jilnjUacett, and Podoitemacea, belonging to the class Exogens, grow in 

 water. Among Endogens, the orders Eutomacea, Naiadaceas or 

 'lt, Pitt'mcett, Alitutacete, &c. consist entirely of water-plants ; 

 whilst one of the largest of the few families into which Cryptogamic 

 Plants are divided, the Alga, consists almost entirely of plants which 

 live in the water. 



For the purpose of studying the distribution of the vegetable 

 kingdom, water-plants are distributed into several groups. One of 

 the first divisions that suggests itself in the study of their forms is 

 derived from the composition of the waters in which they grow. 

 Thus we have those which grow in the saline waters of the ocean, and 

 those which grow in the fresh waters inland. Most of the plant. 1 ! 

 which grow at the bottom of the ocean or float in its waters belong 

 to the family of Alga. [A.LOJK.] There are however many plants 

 not belonging to this order which require the influence of salt-water 

 on the soU on which they grow for their production. Thus species 

 of the genera Saltola, AnaJiaxa, Salicornia, and (llau.r will not grow 

 but where they can fuel the influence of salt-water : hence they have 

 been called I'lmiiu >//;,,.'. These plants are found not only v. h.-re 

 the sea washes, but wherever salt-springs find their way to the surface 

 of the earth. There is another group of plants which have their 

 existence determined by saline waters, but are always found near the 

 ea or on the banks of rivers to which the sea has access. Such are 

 species of Chenopndium, Ileliotropium, Viler, AVi/</ii/i, framoltu, and 

 the Mangrove (Rhizophora). These are called Plantte Littoralet, leu 

 Maritime. 



The largest proportion of Frosh- Water Plants belong also to the 

 natural order Alytr, although by far the most conspicuous specimens 

 In-long to the trills of Kxogeuous and Endogenous plants. As the 

 Hea claim* nearly all the species of the genus Puciu and its allies, so 

 the fresh-water claims the majority of the species of the old genus 

 Cimfrrta and its allies. 



Aquatic Plamlii, in Horticulture, are those which naturally grow 

 in deep water, and are carefully distinguished by the cultivator from 

 marsh-plant*. The management of them, when they are hardy, is of 

 Hi.- rimpli-xt kind, nothing being necessary beyond planting them in 

 boxes with hole* in the sides, and sinking them 3 or 4 feet below 

 the surface of a pond, so that the boxes lie upon or among the mud 

 at the bottom. 



l!ut for thorn which demand the protection of the stove or green- 



. nomo additional precaution* are requisite. If left to them- 



aolve* in such filiations, th uniformity of teiii]MTature is such as to 



measure of the repose that they naturally 



receive from the alternation of seasons ; kept constantly in a growing 

 state, their excitability is gradually destroyed, and death ensue*, aa 

 a matter of course. The plants which demand special treatment 

 are chiefly those which belong to the natum} order NynjJutacea;. 

 [WATER-LILY.] The most beautiful of these is tl, regia. 



Various methods have been recommended ; but they all depend for 

 their success upon keeping in view the principle of periodical rest and 

 rapid growth under a high temperature, with but little air during the 

 Mason of vegetation. 



AQUAVI VAKIUM, a term proposed to be applied to arrangements 

 which contemplate the exhibition of living aquatic specimens of 

 animals inhabiting either fresh or salt water. Although it has been 

 known from the earliest times that animal* living in water may ! 

 kept in small glass vessels for exhibition by the daily supply of 

 fresh-water, the discoveries of modern chemistry have pointed out 

 how animals may be kept living in only limii water 



which never demand renewing. The possibility of accomplishing 

 this depends on the absolute balance in nature which exists b< > 

 the animal and vegetable kingdoms. [AMMAI. KINGDOM.] The one 

 set of these beings are for ever engaged in giving on" what the other 

 requires, and in taking up what the other rejects. It is thus t! 

 carbonic acid which is constantly being thrown off the tissues of 

 animals is taken up by plants, and thus prevented from contaminating 

 the atmosphere ; whilst the plant is constantly engaged in giving o$ 

 oxygen gas, and supplying the atmosphere with this element of its 

 composition which is necessary to the life of animals. The relations 

 which arc thus found to exist on the large scale of the whole M 

 of the earth, are found also to occur in a jar of water. If an animal 

 is placed in pure water it quickly exhausts the oxygen it contains, 

 and gives out into it carbonic acid gas; the consequence is, that it is 

 quickly poisoned unless fresh water with oxygen is supplied. But if 

 we place with the animal some plant that lives in water, it will be 

 found that the carbonic acid given out by the animal will be taken 

 up by the plant, and that it will give out oxygen in its place. Thus 

 the water becomes cleared of its injurious compound, and the needed 

 clement, oxygen, is supplied. This is really what takes place in every 

 pond and pool where the water is fresh, and all that is required to 

 make the inhabitants of the pond visible is to put the whole pond, 

 plant, and animals into a glass-case. Such a plan has been tried with 

 great success, and we propose to call the apparatus in which it is 

 effected an Aquavivariurn. 



The first experiments were made with fresh-water, ami we believe 

 the public is indebted for one of the earliest accounts of such an 

 arrangement to Mr. Warington, chemist to the Apot h< .upany. 



He found out, however, that it was not sufficient to have simply any 

 kind of plants and animals ; but that, in order to maintain the balance 

 correctly, it was necessary that certain animals which lived on <i 

 posing vegetable matter should be present. At certain seasons uf t h- 

 year the tendency to decomposition in the water-plants becom 

 decided that the water would be rendered impure if this decomposition 

 was not arrested. The cure for this was found in the addition of 

 fresh-water Mollusca to the jars containing such fish as the gold-carp 

 and stickleback and such plants as the Vallimeria tpiralit, Call' 

 &c. The best kind of snails for this purpose ore the van 

 of Planorbii. Not only is it necessary that this latter precaution be 

 taken to ensure the success of the experiment, but it is of inqn " 

 to guard against the preponderance of animal life. Although in 

 most cases it appears that there cannot be too many plants for tin- 

 health of the animal as long as they grow healthily and do not 

 decompose, yet it often happens that the excess of animals over 

 plants in a given space will destroy the balance, and le.nl to tin: 

 destruction of life. We are not aware that any precise experiments 

 with regard to the quantity of water and the number of plants and 

 animals have been yet performed. We can however state as a la. t, 

 that a gold-fish has lived for nearly twelve months in ab.mt two gallons 

 of water with several flourishing plants of \'<illitnn>-in tjiii'nlit. It is 

 probable that a smaller quantity of water would have served equally 

 well. 



Amongst the fresh-water plants adapted for growing in such jar: 

 or tanks as we have mentioned, are the VaUuiin-iii x/iii-ti/is, various 

 species of Ckara, Anacluirit Ahinrulrum, Stratiotet Ali<li*. <'<iHHrii-ln- 

 ,iiiiu:i,nalt, C. vernalu, Mi/i-i'i/i/ii/lluiu ;/UVI/KI., and /. 

 ir</H<f/iVu. Such jars afford a good opportunity for cultivating 

 the various species of fresh-water Conferva-, which all assist in 

 keeping the water pure. One of the most beautiful of these 

 Hytlrodictyvn utricutatum, which may be easily propagated in this 

 manner. 



A 11 hough these results have been known for many years, it i 

 recently that any attempts have been made to carry out the same plan 

 with regard to marine animals and plants in sea-water. The only plan 

 adoj,ti-d of keeping the Marine Invertebrate Animals was the lal.on.m, 

 one of supplying them . with water fro m the sea. For 



upwards of thirty years Sir , I. -hn iialyll carried on bin observations 

 on sea-animals in the city of Edinburgh upon this system. It, was 

 however known generally am 



water to the action of tin- air by pouring it fn i \.-s-.-l into 



.inoiher, it became perfectly purified. In this way many persons 

 succeeded in maintaining alive, in the heart of London, .1 



