WEEDS (IF AGRICULTURE. 321 



the soil. On the contrary, it is asserted, that land which 

 has been previously cropped, actually requires bleaching by 

 the sun and air, to fr^e it from noxious exudations discharged 

 by the roots of previous crops ; and which act as poisons to 

 plants of the same species. It is thus that these philosophers 

 account for the difficulty of growing crops of the same kind 

 consecutively : why broad clover, or any other crop, tires 

 of the same field: and moreover, the only cogent reason tiiat 

 can be given fur the necessity of a constant change, or rota- 

 tion of crops. 



There may be some truth in this new philosophy, but it is 

 not yet generally received. Though there can be no doubt of 

 the necessity of fallowing, in order to clear the soil from weeds, 

 or to get it into a proper state for the reception of seed, yet 

 it is a well-known fact, that the more a light soil is ploughed 

 during summer, the less capable is it of bearing a heavy 

 crop of corn, unless recruited by an adequate supply of 

 manure. 



2. REST-HARROW {ononis arvensis). Called also Cam- 

 mock. Flowers axillary, in pairs ; leaves ternate, upper 

 ones solitary ; branches villose. 



I should not have set this down as a fallow weed, had not 

 Mr. William Pitt, of Wolverhampton, mentioned, in his Es- 

 say on Weeds (printed in the 5th vol. of Communications 

 to the Board of Agriculture), that it is common about Wol- 

 verhampton. He adds, "But if the root can be destroyed 

 in the fallow, there is little dano-er from the seeds." Thoug-h 

 Mr. Pitt, by several of his articles, was not an agriculturist, 

 yet he understood botany very well, and must be allowed to 

 know what was common about Woherhampton . There can be 

 no doubt but that the rest-harrow and the thorny rest-harrow 

 {ononis spinosa), were common annoyances to the operations of 

 agriculture a hundred years ago, but I should have thought 

 them now confined to wastes, banks, and warrens. The names 

 petti/ whin nnd g70undfiurze, ^\ven to the thorny species, will 

 indicate to the reader its resemblance to gorse (nlex Euro- 

 pans) ; but the flower is nearly white, and the plant trails 

 on the surface. It is quoted by Dr. Withering, from 



Y 



