PLANTS AND THEIR CULTURE. 105 



We have already spoken of it as a manure ; and 

 we take this occasion to quote from a late editor of 

 the Theatre d'Agriculture of 0. Serres, the follow- 

 ing passage : " We cannot too much recommend, 

 after our old and constant practice, the employ- 

 ment of this precious plant as a manure. It is 

 certainly the most economical and convenient the 

 farmer can employ. A small quantity of seed, cost- 

 ing very little, sows a large surface and gives a great 

 crop. When in flower, first roll and then plough it 

 in. Its shade, while growing, destroys all weeds, 

 and itself, when buried, is soon converted into ter- 

 reau."* 



The experiments of M. Vauquelin show that, of 

 one hundred parts of buck wheat, fifty are carbonate 

 and sulphate of potash, and carbonate of lime. 



CHAPTER X. 



OP OTHER PLANTS USEFUL IN A ROTATION OF CROPS, 

 AND ADAPTED TO OUR CLIMATE. 



THESE may be brought under three classes ; those 

 which yield a colouring matter, those which yield 

 oil, and those whose bark is convertible into cloth- 

 ing. Of the first are madder, saffron, and woad ; of 

 the second, poppy, colet, and palma Christi ; and of 

 the third, flax and hemp. 



I. Of Madder. 



Madder is the erythros of the Greeks, and the ru- 

 bia of the Latins, so called from its imparting a red 

 colour to wool and leather. It is cultivated in the 

 Levant, in France, in Flanders, and in England ; but 

 nowhere more extensively or profitably than in 



* Vegetable mould. 



