74 HOW SEEDS "COME UP" 



3. How do onions come up through the soil? To which 

 type of plants does the onion belong? 



4. What is the chief condition of the soil that guides us 

 in depth of planting? 



5. Quack grass has so strong a growing point in the soil 

 that it has been found to pierce a potato in the ground. 

 Why does this make it a particularly harmful weed? 



