480 THE BEAN PLANT. [CHAP. 



the two large fleshy cotyledons of the embryo will 

 be laid bare. Joining the cotyledons together 

 will be found the rest of the embryo : it consists 

 of a conical part (the radicle) lying outside the 

 cotyledons, with its apex directed towards the 

 point where the micropyle was : and of the rudi- 

 ments of the stem and leaves (pliwiule) lying 

 between the cotyledons. 



g. The process of fertilization. 



This is difficult to follow in the bean; but by using 

 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 {CEiiol/iera bietuiis). 



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 Verofiica. 

 The common V. serpylUfolla — often to be found 

 in shady places on lawns — is well adapted for the 

 purpose. A flower should be taken from which the 



