HOW CHARACTERS ARE TRANSMITTED 



123 



in good time develop inlo a single kernel of corn ; but if all 

 does not go well, the silk will grow longer for a time, and finally 

 wither away, but the kernel will not develop, and nothing but a 

 bare cob will be found at husking time. What is it that decides 

 whether there is to be or is not to be a kernel ? The answer 

 to that question involves the whole machinery of transmission. 



Ever)' farmer boy knows 

 that at the top of the stalk 

 is the tassel, and that this 

 tassel has the habit at times 

 of shedding large amounts 

 of yellow powder, particu- 

 larly after a rain or in the 

 still hours of the early morn- 

 ing after a warm but quiet 

 night. Most farmer boys 

 know that in some way this 

 golden-yellow dust, or "pol- 

 len," is connected with the 

 crop, but few of them know 

 in just what way. 



Fig. 18. Ear covered for ten days with a 

 paper sack preventing fertilization. The 

 silk remained fresh and continued to grow. 

 It has been known to reach a length of 

 two feet while awaiting the pollen 



If we use a microscope to magnify size, and see exactly what 

 is involved and what is going on, it would be somewhat as 

 follows : 



First of all, the silk would be found to be soft and pulpy 

 throughout its entire length, somewhat " sticky " and branched 

 at the top or outer end, and connected at the base with a single 

 cell, called an ovule.^ Now this ovule is the important part, for 

 it is what develops into the kernel of corn if all goes well. 



* A " cell " is the structural unit of the plant or animal. As a building is 

 made of bricks, so the plant or animal body is made up of cells or sacks filled 

 with a semifluid matter known as protoplasm, which is a kind of general name 

 for the material of different parts of the body ; that is to say, the protoplasm 

 of muscle, whose business it is to contract, is quite different from the proto- 

 plasm of liver, whose busine.ss it is to manufacture a definite secretion. The 

 cells of different parts of the body structure contain, therefore, very different 



