94 CIRCULATION AND USES OF PLANT FOOD 



and protecting the embryo within the body of the mother until it 

 is born, a helpless little creature, to be tenderly nourished by the 

 mother until able to care for itself. 



Life History. — Ultimately both plants and animals grow old 

 and die. Some plants, for example the pea or bean, live but a 

 season ; others, such as the big trees of California, live for hundreds 

 of years. Some animals, certain insects, exist as adults but a day, 

 while the elephant is said to live almost two hundred years. The 

 span of life from the time the plant or animal begins to grow until 

 it dies is known as its life history (or sometimes its life cycle) . 



Pkoblem Questions 



1. What proof have we of the passage of water and food substances up and 

 down the stem ? 



2. How do "monocot" and "dicot" stems differ? 



3. How does a stem get air? 



4. What causes water to rise against gravity in a stem? 



5. How and where are foods digested in plants ? 



6. Where are foods stored, and why ? 



7. What are the life processes of a green plant? 



8. Of what value are green plants to man ? 



Problem and Project References 



Hunter, Laboratory Problems in Civic Biology. American Book Company. 



Densmore, General Botany. Ginn and Company. 



Dana, Plants and Their Children, pages 99-129. American Book Company. 



Duggar, Plant Physiology. The Macmillan Company. 



Coulter, Barnes, and Cowles, A Textbook of Botany, Vol. I. American Book 



Company. 

 Gager, Fundamentals of Botany. P. Blakiston's Son and Company. 

 Ganong, The Teaching Botanist. The Macmillan Company. 

 Mayne and Hatch, High School Agriculture. American Book Company. 

 Hodge, Nature Study and Life, Chaps. IX, X, XI. Ginn and Company. 

 Transeau, General Botany. World Book Company. 

 United States Department of Agriculture, Yearbooks, for project work. 



