NUMBER OF POLLEN GRAINS TO EACH OVULE 145 



pollen grains for 30,000 ovules, or rather more than 8 to 1 ; 

 in the common garden wistaria there are about 7000 pollen 

 grains to every ovule, and in Indian corn, the cone-bearing 

 evergreens, and a multitude of other plants, there are many 



E 



FIG. 158. First stages in the development of the egg cell of the 

 European ivy (Hedera Helix) 



A, egg cell. B : s, cell which will form the suspensor; e, cell which will form the 

 embryo. C, showing first subdivision of the suspensor-forming cell ; Z>, show- 

 ing subdivision of the embryo-forming cell; E, showing subdivision of both 

 regions, slightly more advanced. After Bonnier and Sablon 



times more than 7000 to 1. These differences depend upon the 

 mode in which the pollen is carried from the stamens to the 

 pistil. Plants which are pollinated by the wind must produce 

 far more pollen, to allow for inevitable waste, than those which 

 are self-pollinated, or pollinated by insects (Chapter xxxn). 



