PLANTS AND INSECTS 



FIG. 75. Flower of Bartlett 

 pear natural size. (After 

 Waite.) 



pollen escapes from the anthers of the same flower. The 

 stigma often extends through the petals before they are 



fully open, thus offering the 

 possibility of pollination from 

 some earlier blossoming variety, 

 - another way for cross-fertili- 

 zation to occur. 



The process of fecundation 

 Waite describes : " Soon after 

 its protrusion the stigma se- 

 cretes a sugary fluid, often in 

 sufficient quantity to be quite 

 perceptible. In this the pollen 

 grain readily germinates and throws 

 out a slender, thread-like tube, which 

 grows downward into the pistil and 

 through specially soft tissue, adapted 

 to its growth, until it reaches the ovules. 

 Here it enters an opening in the two 

 outer coats of the ovule and conies in 

 contact with the germ-cell, or egg- 

 cell. A number of inter- 

 esting and complicated 

 changes now take pla.ce natural size, 

 in the protoplasm of this cell and in the 

 end of the pollen tube. A part of the con- 

 tents of the latter actually passes through 

 the cell-walls into the egg-cell, which, un- 

 der this stimulus, immediately begins to 

 showing only the <> T < , w and divide, ultimately developing 



five pistils nat- '. 



into the germ of the seed. This stim- 



FIG. 76. Bud of 

 the Bartlett pear, 

 with the petals re- 

 moved, showing the 

 incurved stamens 



