50 



FUNCTIONS OF LIVING THINGS 



Diagram Showing Cells. 

 N, nucleus ; P, protoplasm ; W, walls. 



Observations. — What is the 

 shape of a single cell? Are 

 all cells examined the same 

 size? Shape? Can you lo- 

 cate the nucleus (a deeply 

 stained body) , cytoplasm (pro- 

 toplasm outside the nucleus), 

 and cell wall? Any other 

 structures ? 



Are the cells separate or 

 united with one another? 



Note. — Cells of the same sort joined together in a plant or an animal form 

 tissues. Tissues are grouped in both plants and animals to form organs, struc- 

 tures which have some certain work to do, as a leaf, a root, a hand, an eye, etc. 



Conclusion. — 1. In the onion do the cells form tissues? Give 

 reason for your answer. 



2. What are tissues ? Of what are tissues composed ? 



3. What are organs? Give examples from your own body. 



4. Define a cell from what you have seen under the microscope. 



5. (Optional.) Draw a few of the cells stained with methyl 

 blue or iodine, showing cell walls, nuclei, and protoplasm. 



Pi^obletn 20 : To determiiie some of the properties of proto- 

 plasm. 



Materials. — Stamen hairs of spiderwort {Tradescantia) , leaves 

 of Elodea, or the root hairs of radish or grain seedlings are useful. 

 As Elodea is easily grown in aquaria, it is recommended for this 

 exercise. 



Observations. — Examine a bit of mounted leaf of Elodea. 

 What is its general appearance under the low power? Can you 

 locate individual cells in the mass ? Note the green bodies in the 

 cells {chlorophyll bodies) . Can you find the cell walls ? The liv- 

 ing matter (protoplasm) ? 



Look closely along the edge of the cells for any movement of 

 living matter within the cell. Does the protoplasm move in any 

 particular direction? 



