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MA12E 



CHAP, the stigmatic hairs of the silk or style, it begins to grow. The 

 pollen grain takes up moisture from the stigma and begins 

 to swell ; a tube, called the pollen tube, pushes out from one 

 side of the pollen grain, penetrates the silk, and grows down 

 its whole length till it reaches the ovary at the base (Fig. 53). 



Fig. 53. — Diagram showing course of pollen tube through style to ovule. 



A, Section near outer end of style, showing pollen grain (a) and pollen tube (g). 



B, Section through base of silk and through ovule (e). (After drawing by C. S. 

 Ridgway, in Duggar's Southern Field Crops, New York, The Macmillan Co.) 



Into this tube the contents of the pollen grain, including the 

 nuclei, pass. During growth the vegetative nucleus becomes 

 gradually disorganized and is lost in the protoplasm. The 

 generative nucleus, however, has divided and formed two 

 nuclei. On reaching the ovary, the pollen-tube enters the 

 embryo-sac, and discharges its two nuclei; one of these fuses 



