Book I. DISTRIBUTION OF VEGETABLES. 201 



result is, as De Candolle has well remarked, that it is often a very bad method of cul- 

 ture to imitate too exactly the nature of the earth in which a plant grows in its wild 

 state. 



928. Mixed or secondary soils include not only primitive earths, or the dtbrls of rocks, 

 but vegetable matters not only the medium through which perfect plants obtain their 

 food, but that food itself. In this view of the subject the term soil is used in a very ex- 

 tensive acceptation, as signifying, not only the various sorts of earths which constitute the 

 surface of the globe, but every substance whatever on which plants are found to vegetate, 

 or from which they derive their nourishment. The obvious division of soils in this ac- 

 ceptation of the term is that of aquatic, terrestrial, and vegetable soils ; corresponding 

 to the division of aquatic, terrestial, and parasitical plants. 



929. Aquatic soils are such as are either wholly or partially inundated with water, and 

 are fitted to produce such plants only as are denominated aquatics. Of aquatics there 

 are several subdivisions according to the particular situations they affect, or the degree 

 of immersion they require. 



One of the principal subdivisions of aquatics is that of marine plants, such as the fuci and many of the 

 algae, which are very plentiful in the seas that wash the coasts of Great Britain, and are generally at- 

 tached to stones and rocks near the shore. Some of them are always immersed ; and others, which are 

 situated above low water mark, are immersed and exposed to the action of the atmosphere alternately. 

 But none of them can be made to vegetate except in the waters of the sea. Another subdivision of aqua- 

 tics is that of river plants, such as chara, potamogeton, and nymphaea, which occupy the bed of fresh 

 water rivers, and vegetate in the midst of the running stream ; being for the most part wholly immersed, 

 as well as found only in such situations. 



A third subdivision of aquatics is that of paludal or fen plants, being such as are peculiar to lakes, 

 marshes, and stagnant or nearly stagnant waters, but of which the bottom is often tolerably clear. In 

 such situations you find the isoetes lacustris, flowering rush, water ranunculus, water violet, and a variety 

 of others which uniformly affect such situations j some of them being wholly immersed, and others im- 

 mersed only in part. 



930. Earthy soils are such as emerge above the water and constitute the surface of the 

 habitable globe, that is every where covered with vegetable productions. Plants affecting 

 such soils, which comprise by far the greater part of the vegetable kingdom, are de- 

 nominated terrestrial, being such as vegetate upon the surface of the earth, without having 

 any portion immersed in water, or requiring any further moisture for their support 

 beyond that which they derive from the earth and atmosphere. This division is, like the 

 aquatics, distributed into several subdivisions according to the peculiar situations which 

 different tribes affect. 



931. Some of them are maritime, that is, growing only on the sea-coast, or at no great distance from 

 it, such as statice, glaux, samolus, samphire, sea-pea. 

 932 Some are fluviatUe, that is, affecting the banks of rivers, such as lythrum, lycopus, eupatorium. 



933. Some are champaign, that is, affecting chiefly the plains, meadows, and cultivated fields, soch as 

 cardamine, tragopogon, agrostemma. 



934. Some are dumose, that is, growing in hedges and thickets, such as the bramble. 

 !)35. Some are ruderaie, that is, growing on rubbish, such as senecio viscosus. 



936. Some are sylvatic, that is, growing in woods or forests, such as stachys sylvatica, angelica sylvestris. 



937. And, finally, some are alpine, that is, growing on the summits of mountains, such as poa alpina, 

 epilobium alpinum, and many of the mosses and lichens. 



938. Vegetable soils are such as are formed of vegetating or decayed plants themselves, 

 to some of which the seeds of certain other plants are found to adhere, as being the only 

 soil fitted to their germination and developement. The plants springing from them are 

 denominated Parasitical, as being plants that will vegetate neither in the water nor earth, 

 but on certain other plants, to which they attach themselves by means of roots that 

 penetrate the bark, and from the juices of which they do often, though not always, derive 

 their support. This last circumstance constitutes the ground of a subdivision of parasiti- 

 cal plants, into such as adhere to the dead or inert parts of other plants, and such as ad- 

 here to living plants, and feed on their juices. 



939. In the first subdivision we may place parasitical mosses, lichens, and fungi, which are found as 

 often, and in as great perfection on the stumps of rotten trees, and on rotten pales and stakes, as on tree3 

 that are yet vegetating ; whence it is also plain that they do not derive their nourishment from the juices 

 of the plants on which they grow, but from their decayed parts, and the atmosphere by which they are 

 surrounded ; the plant to which they cling serving as a basis of support 



940. In the second subdivision we may place all plants strictly parasitical, that is, all such as do actually 

 abstract from the juices of the plant to which they cling the nourishment necessary to the developement 

 of their parts ; and of which the most common, at least as being indigenous to Britain, are the Misletoe, 

 Dodder, Broom-rape, and a sort of tuber that grows on the root of Saffron, and destroys it if allowed to 

 spread. 



941. The Misletoe ( Viscum album) is found for the most part on the apple-tree ; but sometimes also on 

 the oak. If its berry is made to adhere to the trunk or branch of either of the foregoing trees, which 

 from its glutinous nature it may readily be made to do, it germinates by sending out a small globular body 

 attached to a pedicle, which after it acquires a certain length bends towards the bark, whether above it or 

 below it, into which it insinuates itself by means of a number of small fibres which it now protrudes, and 

 by which it abstracts from the plant the nourishment necessary to its future developement When the 

 root has thus fixed itself in the bark of the supporting tree, the stem of the parasite begins to ascend, at 

 first smooth and tapering, and of a pale green colour, but finally protruding a multiplicity of branches and 

 leaves. It seems to have been thought by some botanists that the roots of the Misletoe penetrate even 

 into the wood, as well as through the bark. But the observations of Du Hamel show that this opinion is 

 not well founded. The roots are indeed often found within the wood, which they thus seem to have 



