72 THE DEVELOPMENT OF RAW COTTON 



brown on exposure to light. From the twenty-seventh 

 to forty-fifth day, however, the pickle thus made is at 

 first pink, and then bright red. The colour is probably 

 connected with the development of pigment in the seed- 

 coat. When the boll is beginning to crack, the pickle is 

 brown. 



By the thirty-third day the palisade layer would 

 appear to have reached its limit of possible extension by 

 the method of construction practised thus far, and it 

 finishes by putting down a certain amount of thick cell 

 wall externally to its nuclei, so that in the ripe seed the 

 palisade layer, which comprises half the total thickness 

 of the seed-coat, shows a granular zone running through 

 it at about one-third of the way inwards. This zone is 

 the dead remains of the nuclei and protoplasm, which 

 thus constructed and sealed their own living tomb. 



At the same stage the epidermis has finished enlarg- 

 ing, and has begun to thicken its walls. 



Subsequent changes are relatively uninteresting. The 

 inner epidermis of the outer seed-coat thickens its walls 

 without marked alteration otherwise, and the cells which 

 separate it from the outer epidermis are disorganized to 

 form the outer pigment layer of the ripe seed. 



All the cells lying within the palisade layer are similarly 

 disorganized, forming the second pigment layer, the inner 

 epidermis of the inner coat disappearing along with thdm, 

 in marked contrast to the enormous palisade layer formed 

 from the outer epidermis. 



It has seemed worth while to give the details of seed- 

 coat development at some length, because of the casual 



