296 CHYMISTRY APPLIED TO AGRICULTURE. 



night soil, the dung of sheep and doves, the decayed frag- 

 ments of wool and silk, and the chrysalises of the silk-worm, 

 are preferred to any other manures. 



Those substances that act as stimulants to vegetation, 

 such as lime, plaster, marine salt, poudrette, mortar-rub- 

 bish, ashes, &lc. favor the growth of the plant without affect- 

 ing the coloring principle. 



When land has been dressed with barn-yard manure, it 

 may be made to yield a crop of grain or maize, and after- 

 wards be sown with woad. 



The season for sowing the isatis varies much in different 

 parts of Europe. In Italy, Corsica, Tuscany, &,c. it is 

 sown in the course of the month of November. As it does 

 not receive injury from the cold, it grows during the winter, 

 and in March is sufficiently strong to overcome the weeds 

 which usually make their appearance at that season. From 

 the circumstance of its growing through the winter, it may 

 be rendered a very important article of nourishment for 

 horned cattle. 



In the south of France, woad is sown in March, and in 

 England in February. In certain other countries it is sown 

 after the corn harvests ; but in this case, a season favorable 

 to vegetation is required, and the practice of sowing at that 

 time can only be followed advantageously in those climates 

 where rains are certain, so that the cultivator may be able to 

 gather two or three harvests of leaves before winter. His 

 fields of woad will afford him pastures for his cattle during 

 the frosts, and he is secure at the return of summer of an 

 abundant harvest of leaves. 



The seed of the isatis should be soaked in water previ- 

 ously to sowing, as germination will be hastened by it. The 

 seed is sown broadcast, in the same quantity as wheat, and 

 harrowed in. The blade shows itself at the end of ten or 

 twelve days. As soon as the plants have thrown out five 

 or six leaves, they must be carefully weeded, and this must 

 be repeated several times before gathering the leaves. The 

 design of the weeding is to remove all strange plants that 

 may spring up in the same soil, especially the roots of bas- 

 tard woad, (bourdaigne), the mixture of which injures the 

 coloring matter of the pure isatis; and to thin the rows 

 of stalks, that those remaining may have more room to 

 grow. 



The isatis, like other plants, has its diseases and its 

 enemies. The leaves are fi-equently seen covered with 



