THE NATURE AND NEEDS OF LIVING MATTER 35 



7. Make the image entirely clear by a slight turn of the fine adjust- 

 ment to one side or the other. 



a. Study of Cells and Starch Grains 



Direction. Study the cellulose walls inclosing spaces in which lie 

 the deeply stained starch grains. 



1. What color does cellulose show under the microscope ? 



2. What color is shown by starch grains treated with iodine ? 



b. Study of a Drop of Milk (an Emulsion) 



1. Place drop of milk on slide. Cover with slip. Notice the small 

 globules of fat floating in a liquid. Are all these of the same size ? ' 



2. Are they equally abundant in all parts of the field ? 



Note. A liquid containing large numbers of tiny fat droplets is called 

 an emulsion. 



3. Shake some olive oil and water together in a test tube. What is the 

 color ? Appearance ? 



PROBLEM V 



The structure and general properties of living matter. 



a. General Structure 



1. SINGLE CELLS 



Method. Scrape off some of the green " dust " so commonly 

 seen on the north sides of trees and allow it to stand in water 

 for a day or two. Mount some in a little water and study with 

 the compound microscope, 1 first using low power, then high 

 power. ( 2 Dem.) Optionally use any one-celled alga, as desmids. 



Observations. 1. What is the color of a single plant (cell)? 

 Form ? 



2. Are the cells alike? If not, what differences ? 



3. Do you find any cells splitting into two or four parts ? 



1 Much may be accomplished by setting one microscope so that pupils may 

 see the demonstration in turn while the rest are studying charts, references, 

 etc., or making sketches, at the discretion of the teacher. 



2 Dem. indicates a demonstration by the instructor. Here introduce a short 

 3tudy of the use of the microscope. See Exercise, page 32. 



