STRUCTURE OF THE BOLL 67 



boll in ten has only two divisions instead of three, this 

 peculiarity of the strain being a useful mark. The 

 ovary from which it develops is about 5 millimetres in 

 diameter. 



The yellow petals having faded during the afternoon 

 of the day of flowering, they wither and dry up during 

 the first day of the boll history, and on the second or 

 third day have usually fallen off, carrying with them the 

 faded brush of stamens, and breaking away the remains / 

 of the style. This cutting off of the petals is effected by 1 ' 

 the differentiation of a layer round their base, the cells 

 of which separate from one another instead of remaining 

 united after division. The process of shedding of the 

 bud, flower, or boll, is effected by the plant in the same 

 way, the layer of special cells in this case being formed 

 across the stalk. In both cases there is probably a 

 reaction to some chemical stimulus, normal in the one 

 case, abnormal in the other. Some accepted accounts of 

 cotton inform us that the petals undergo a "peculiar 

 rotation " on their own axis, whereby they " twist them- 

 selves completely off." This is scarcely correct. 



The diameter of the ripening ovary, or boll, has mean- 

 while been increasing rapidly. From some 4 to 5 milli- 

 metres at flowering, it enlarges by about a millimetre of 

 diameter each day. On the sixth day it has a diameter 

 of 1 2 millimetres, or half -size ; on the twelfth day 1 8 milli- 

 metres; and on the eighteenth day 24 millimetres. The 

 figures with this strain are easily remembered, being six 

 more than the number of days. After the eighteenth 

 day the rate is rapidly decreased, and the full diameter of 



