50 



FUNCTIONS OF LIVING THINGS 



DiAGKAM 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. 



Problem 20 : To determine 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? 



