Book VI. 



PLANTS INJURIOUS TO AGUICULTURE. 



947 



in the Cours Complet, <^c. art. Sonde. The ground is brought into good tilth, and 

 manured ; and the seed sown broadcast in October or Novemlier : in the following 

 spring the plants will be found an inch high, and must be kept clear of weeds till the 

 month of August, when, being at its full growth, it may be mown or pulled up (for it has 

 scarcely any roots), dried, and afterwards burnt in holes in the ground like kelp. 



6195. The sea-wrack grass (Zostera marina; Fluviales) is found in abundance on 

 different parts of our own shores, as at Yarmouth, the bays of the Orkney Islands, and 

 other bays not exposed to the immediate fury of the ocean. 



6196. It grows in banks of sand and mud, which banks appear to be held together principally by the roots 

 of this plant, which are strong and succulent, and throw out numerous lateral fibres. It grows at such 

 depths as to be left nearly dry by the ebbing of spring tides. During the autumn and beginning of winter 

 these leaves are thrown on shore in large quantities. They are of a very imperishable nature, and may 

 be kept for any length of time in fresli or salt water, without any apparent decay. In the Orkney Islands 

 this grass is thrown ashore during winter in large quantities, and collected by the inhabitants with other 

 marine plants into heaps, for manure. In these heaps it is allowed to ferment, and sometimes, before 

 being applied, it is mixed with earth or other matters. It is also used as thatch, and forms a more durable 

 defence against the violent winds and heavy rains of that climate than straw. A few years ago, in con- 

 sequence of premiums offered by the Highland Society, this grass was applied as a substitute for horse- 

 hair, and stuffing mattresses and furniture : for this purpose it is carefully washed twice in fresh water, 

 then dried quickly ; and afterwards, any sea-weed that had got mixed with it picked out. In the Orkneys 

 it is steeped in fresh-water lakes for a week, then taken out and spread wet on. the ground, and picked, 

 while in this state, from extraneous matters. Exposure to drought for one day will make it sufficiently 

 dry for packing. Wlien dry, care must be taken, if the weather is windy, to gather it into heaps or cocks, 

 otherwise it may be blown away, being then extremely light. It is sent to market in large bags of sack- 

 ing, or twisted into ropes of the thickness of a man's waist, and then compactly made up in nets, formed 

 of ropes made of bent grass. It is sold at the Asylum for the Industrious Blind at Edinburgh, who era- 

 ploy it in stuffing mattresses. {Highl. Sac. Trans, vol. vi. p. 592.) 



Chap. X. 

 Weeds or Plants injurious to those cultivated in Agriculture. 



6197. JEveri/ plant which appeal's where it is not wanted may be considered injurious, 

 though some are much more so than others. A stalk of barley in a field of oats is a weed, 

 relatively to the latter crop, but a thistle is a weed in any crop ; weeds, therefore, may 

 be classed as relative and absolute. 



6198. Relative vjceds, or such cultivated plants as spring up where they are not wanted, give compara- 

 tively little trouble in extirpating them. The most numerous are the grasses when they spring up in fields 

 of saintfoin or lucern, or among corn crops in newly broken up grass lands. The roots of chiccory, in 

 fields that have been broken up after bearing that crop for some years, those of madder, liquorice, &c., are 

 of difficult extirpation. When the potato crop has not been carefully gathered, or mustard has been 

 allowed to shed its seed, they also occasion trouble. Other cases will readily occur to the practical man, 

 and need not be mentioned. 



6199. Absolute weeds, or such native plants as are considered injurious to all crops, are very numerous, and 

 may be variously arranged. Some affect in a more peculiar manner corn-fields and tillage lands, and these 

 are chiefly annuals, as wild mustard, wild radish, poppy, blue-bottle, cockle, darnel, &c. ; or biennials, as 

 the thistle; or perennials, as couch-grass, knot-grass, black-couch, polygonum, &c. ; on lands laid down 

 to grass for a few years, dock, ox-eye daisy, ragweed, &c. Others infest grass lands, and these are chiefly 

 perennials,, such as crowfoot, one of the most difficult of weeds to extirpate ; thistles, docks, rushes, sedges, 

 moss, and an endless variety of others. Some are more particularly abundant in hedges; of which the 

 reedy and coarse grasses, as couch-grass, brome-grass ; the climbing and twining plants, as goose-grass 

 (Gklium .Sparine) ; and the twiners, as bind-weed (Conv61vulus), are the most injurious. 



6200. With regard to the destruction of weeds, they may be classed first according to 

 their duration. 

 6201. All annuals and biennials, as sai.d-wort (^^.816. a), and sorrel (6), are efFectually destroyed by 



816 



cutting over the plant at anypoint below that whence the seed 

 leaves originated, as this prevents them from ever springing 

 again from the roots. Perennials of the fibrous-rooted kind 

 may be destroyed in the same manner, as the crowfoot, rag- 

 weed, the fibrous-rooted grasses, and many others. Some 

 fusiform-rooted perennials may also be destroyed by similar 

 means ; but almost all the thick-rooted perennials require to be 

 wholly eradicated, 



6202. The perennial weed;, which require their roots to be 

 wholly eradicated, may be classed according to the kind of 

 roots. The first we shall mention are the stoloniferous roots or 

 surface shoots of plants, by which they propagate themselves. 

 Of this kind are the creeping crowfoot, goosefoot or wild 

 tansy, potentillas, mints, strawberries, black couch-grass, and 

 most of the Jgrostidea^ and other grasses. The next are the 

 under-ground creeping roots, as the couch-grass. Convolvulus 

 arvensis, and other species of bind-weed, coltsfoot (Jig. 816. c), 

 sowthistle, several tetradynamous plants, as toadflax, Scrophu- 

 l^ria, nettle, hedge-nettle (Stkchys), iamium, ^allota, &c. 

 Some of these, as the bihdweed and corn-mint, are extremely 

 difficult to eradicate : a single inch of stolone, if left in the 

 ground, sending up a shoot and becoming a plant. The creep- 

 ing and descending vivacious roots are the most difficult of 

 all to eradicate. Of this class are the Polygonum amphibium 

 (Jig. 817. a), the reed (^rAndo Phragmites), the horse-tail 

 lEqm&htum,Jig.8n.b), and some others. These plants abound 

 in deep clays, which have been deposited by water, as in the 

 carses and clay-vales of Scotland. In the Carse of Falkirk for 

 example, the roots of the Polygonum amphibium are found 

 3 P 2 



