LABORATORY EXERCISES 33 



sperm, taste of pith and kernels. These are but a few of the many 

 characters that may be compared. 



2. Galton's Law. 



Measure 100 or more plants of any kind, arrange the results in 

 order and draw a curve representing the measurements. The height 

 of 100 corn-stalks, length, weight, or circumference of 100 ears of corn, 

 or any kind of measurements may be used. 



3. Struggle for Existence. 



Materials. An ear of corn for each student, also a purslane plant, 

 pigweed or other weed with many seeds. How many kernels on the 

 ear of corn? Count one row and multiply by the number of rows. 



How many seeds on the pigweed, or other plant? Count the seeds 

 on a few branches and multiply by the number of branches. 



Begin with one kernel of corn, or one pigweed seed, and suppose 

 that each grew and developed as these have done. How many would 

 there be in three years? 



4. Struggle for Existence. 



Field Trip. (1) Go to a weed "patch." Let each student take 

 one square foot or more of area. Count all the plants on this area. How 

 many are apparently not going to be able to form seeds? 



(2) Examine an unpruned tree. What proportion of the branches 

 have been killed by crowding out? Count the buds on a twig. How 

 many can develop into branches? 



(3) If a woodlot where trees grow naturally is available, visit it. 

 Find trees that have been killed. What proportion survive? Find 

 those that are overshadowed, but that are still alive waiting for a 

 chance. Compare their ages with the large trees. 



5. Struggle for Existence among the Buds of a Potato. 

 Materials. Potato and dish of water. 



Place a potato in a glass of water so that the stem end touches 

 the water, and allow it to grow. How many "eyes" start? After these 

 have grown some time, cut them out and see if the others start. 



6. The Flowers of Some Crops. 



Materials. The flowers of such farm crops as grow in the neighbor- 

 hood: Corn, oats, wheat, rye, rice, cotton, etc. Dried specimens may 

 be used, but materials preserved in formalin are better; fresh material 

 is the best. 



