Weed, a term applied to all, rank, coarse vegetables, that grow spontaneously, to the detriment of other plants.

Weeds are usually divided into two classes, namely, annual, and perennial. With a view to eradicate the former, it will be advisable to plough them up, shortly before their seeds are formed, or at least previously to their attaining to a state of maturity. - The small seeds of weeds, that are parated in winnowing grain, ought to be carefully burnt; because, when thrown upon dung-hills, and afterwards spread on land among manure, they vegetate with increased luxuriance.

Perennial weeds are exterminated with the greatest difficulty; as they strike very deep rout. The usual method of extirpating them, is that of bringing them to the surface by the plough ; after which they are gathered by hand i but, as this mode is very expensive, it will be more advantageous to cut them half-through, about the middle of June, or when they are in full vigour: for the sudden interruption of their circulating sap causes that fluid to .stagnate in the roots; in consequence of which the plant generally perishes: thus, such weeds may be collected by means of Mr. Sandilands' Wrack-Har-row, (see vol. ii. p. 432) ; then burnt, and strewed on the land by way of ManuRe. - See also vol. iii.

Weeds often abound in the beds of navigable canals and rivers. As their eradication, however, is tedious, and sometimes occasions considerable expence, M. De Betan-Court Molina, in 1796, pre-sented to the Society for the Encouragement of Arts, etc. a model of a machine designed to mow or rut them, so that they may then be carried down with the stream; or, if the current be not sufficiently id for that purpose, they may be collected on the surface of the water, and employed as manure this contrivance, he was rewarded with the premium of forty guineas ; but, as a plain description would not convey an adequate idea of the principles on which it instructed, we refer the reader to the ; 4th volume of the " Tran-actions" of that Society, where a complete account is inserted, and illustrated with an engraving.