298 CHYMISTRY APPLIED TO AGRICULTURE. 



The manufacturers of woad cakes govern themselves 

 upon this subject according to their own observations, and 

 their modes of procedure vary more or less in different 

 countries. 



In England and Germany, the leaves are cut as soon as 

 they begin to droop, and their bluish color to degenerate 

 into a pale green. 



In Thuringia, the leaves are gathered when they begin 

 to droop, and to give out a strong, penetrating odor. 



In Tuscany, the time for cutting the leaves is judged 

 of by the color which a leaf affords when pressed between 

 two linen cloths. 



In the Roman states, the leaves are considered to be 

 matured when they lose the intensity of their color,= and 

 begin to fade. 



In Piedmont, the leaves are gathered when they begin 

 to fall. 



In the south, the leaves are considered as being mature, 

 when they exhibit a violet shade upon their borders. 



We are indebted to M. Giobert, of Turin, for an ex- 

 cellent treatise upon woad, in which he states that, ac- 

 cording to his observations, the quantity of indigo con- 

 tained in the leaves of the plant in the most favorable 

 seasons, increases progressively from the eleventh to the 

 sixteenth day of their vegetation, after which time it re- 

 mains stationary during four or five days, and then be- 

 gins to decrease. The observations of M. Giobert have 

 been confirmed in the south of France, at Bedford, and in 

 nearly all Italy ; and from them may therefore be deduced 

 a general rule, by which the cutting of the leaves of woad 

 may be governed, whenever the vegetation of the plant 

 has been favored by the combined action of a. good soil, 

 a warm atmosphere, and a suitable degree of moisture ; 

 for without this the leaves will not have reached maturity 

 in twelve or sixteen days, and they should not be gathered 

 before approaching that state. 



The extraction of the indigo is uniformly performed 

 with more ease at an earlier period of vegetation, than 

 when the leaves are perfectly mature ; the quantity of 

 coloring matter obtained is equally great, and the hue of 

 it is handsomer. 



The leaves of the isatis are gathered by plucking them 

 off with the hand, or by cutting the stalks with a knife 

 or pair of scissors ; but whichever way is practised, care 



