SCIENCE OF AGRICULTURE. 



Part II. 



attacheil to the 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 nymphasa, 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 onlv in such situations. 



1710. A third subdivision of aquatics is that oi 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 isoctis lacustris, flowering rush, water ranunculus, water violet, and a 

 variety of others which uniformly affect such situations ; some of them being wholly immersed, and others 

 immersed only in part. 



1711. Earthy soils are such as emerge above the whaler 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 denominated 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. 



1712. 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. 



1713. Some are Jluviatic, that is, affecting the banks of rivers, such as lythrum, lycopus, eupatrorium. 



1714. Some are champaign, that is, affecting chiefly the plains, meadows, and cultivated fields, such as 

 cardamine, tragopogon, agrostemma. 



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



1716. Some are ruderate, that is, growing on rubbisli, such as senecio viscosus. 



1717. Some are sylvatic, that is, growing in woods or forests, such as stachys sylvatica, angelica sylvestris, 



1718. And, finally, some are alpine, that is, growing on the summits of mountains, such as poa alpina, 

 epilobiura alpinum, and many of the mosses and lichens. 



1719. Vegetable .soi/s are such as are formed of vegetating or decayed plants them- 

 selves, 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 

 parasitical plants, into such as adhere to the dead or inert parts of other plants, and such 

 as adhere to living plants, and feed on their juices. 



1720. 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 trees 

 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. 



1721. 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 mistletoe, 

 dodder, broom-rape, and a sort of tuber that grows on the root of saffron, and destroys it if allowed to 

 spread. 



1722. The mistletoe ( 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 num- 

 ber 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 tlie para- 

 site 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 mistletoe penetrate 

 even into the woo<l, 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 penetrated by 

 their own vegetating power. But the fact is, that they 

 are merely covered by the additional layers of wood that 

 have been formed since the fibres first insinuated themselves 

 into the bark. 



1723. The Cuscuta curopcsa, or dodder {fig. 242.), though 

 it is to be accounted a truly parasitical plant in the issue, is 

 yet not originally so. For the seed of this plant when it 

 has fallen to the ground takes root originally by sending 

 down its radicle into the soil and elevating its stem into 

 the air. It is not yet, therefore, a parasitical plant. But 

 the stem which is now elevated above the surface lays hold 



of the first plant it meets with, though it is particularly , ^ , ,., 



partial to hops and nettles, and twines itself around it, attaching itself by means of little'parasitical roots 

 at the points of contact, and finally detaching itself from the soil altogether by the decay of the original 

 root, and becoming a truly parasitical plant. "Withering describes the plant in his arrangement as being 

 originally parasitical ; but this is certainly not the fact. 



1721.. The Orobanche, or broom-rape, which attaches itself by the root to the roots of other plants, is 

 also to be regarded as bemg truly parasitical, thougli it sometimes sends out fibres which seem to draw 

 nourishment from the earth. It is found most frequently on the rcote of clover and common broom. 



