''III-I THE BEAN-PLANT. 85 



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 put- 

 ting on a covering-glass. 



The triangular grains of pollen will be seen sending 

 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. SerpyllifoUa — often to be found in 

 shady places on lawns — is well adapted for the pur- 

 pose. 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 

 that after some time the embryo-sac can be seen and 

 the progress of the pollen-tube into the ovule followed. 



3. The young fruit of Campanula, (especially the com- 

 mon Canterbury Bells of gardens, Campanula Medium) 

 is convenient for examining the embryo-sac. It is 

 only necessary to cut thin transverse sections of the 

 fruit and examine in water. Some of the ovules cut 

 through will allow the embryo-sac to be seen, and in 

 fortunate sections the embryo-vesicle and the end of 

 the pollen-tube in contact with the embryo-sac. 



