viii.] THE BEAN-PLANT. 87 



g. The process of fertilization. 



This is difficult to follow in the bean; but bv usini? 



f O 



different plants for the observation of its various stages 

 it is fairly easy to observe all its more important steps. 



1. A plant well adapted for seeing the penetration of 

 the pollen-tube into the stigma and style is the 

 Evening Primrose ((Enothera biennis]. 



Detach the style from the flower and hold the 

 club-shaped stigma between the finger and thumb 

 of the left hand. Moisten it with a drop of water 

 and then make with a wetted razor several successive 

 cuts through it. This will divide the stigma into 

 several slices. Spread these out on a glass slide 

 with a needle in water and examine the thinnest, 

 after putting on a covering-glass. 



The triangular grains of pollen will be seen send- 

 ing out from one angle a tube into the stigmatic 

 tissue, which is easily seen from its slight difference 

 in colour. 



2. The entrance of the pollen-tube into the micropyle 

 can be readily made out in some species of Veronica. 

 The common V. serpyUifolia - - often to be found 

 in shady places on lawns is well adapted for the 

 purpose. A flower should be taken from which the 

 corolla has just dropped. Dissect out the minute 

 ovary and, using the dissecting microscope, open 

 with a needle one of its two cells in a drop of water ; 

 remove the mass of ovules and gently tease them 

 apart. Then put on a covering-glass and examine 

 with a low power till an ovule is found which shews 

 the entry of the pollen-tube. The addition of dilute 

 glycerine will make the ovule more transparent, so 



