STRUCTURE OF THE BOLL 65 



The history of the fruit proper may be taken as be- 

 ginning with pollination, or perhaps with fertilization of 

 the egg-cell. 



The flower having opened completely by nine or ten 

 o'clock, is pollinated shortly afterwards. By the after- 

 noon of the following day the egg-cell has been fertilized, 

 and is in a resting state. The first day is thus marked 

 by fertilization (Fig. 11, B, b). 



On the third day this resting egg begins to divide into 

 two cells (Fig. 11, B, c), which again divide, and continue 

 to do so, till at the end of a week the embryo is visible 

 under the microscope as a body beginning to show a 

 heart-shaped outline, about 001 millimetre long, and 

 therefore scarcely visible to the naked eye. From this 

 its increase in size continues rapidly, till at the end of the 

 fourth week it has completely filled the seed (Fig. 11, B, I). 



Meanwhile the seed has also been enlarging, and in 

 rather less time has attained its full and final dimensions. 



The boll also reaches its full length and diameter in 

 this period, and the lint, which began to sprout from the 

 seed - coat on the day when the flower opened, has 

 attained its full length. 



The period of maturation, from the opening of the 

 flower to the opening of the boll, being forty-eight days 

 in the case of strain No. 77 at Giza, the boll thus appears 

 to be fully grown at the end of twenty-four days. In the 

 remaining twenty days, however, much remains to be done 

 in the way of structural differentiation. The seed-coat 

 hardens to protect the embryo, the embryo differentiates 

 its internal structures ready to begin an independent 



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