CELL DIVISION 41 



holding it in a warm hand for a few seconds. Other stimuli have 

 other effects depending upon the sensitiveness of the particular cell. 

 Cell division. A plant cell has a certain limit of size beyond 

 which it does not grow. When this limit is reached, the nucleus 

 may elongate and divide, producing two nuclei. There is a wall 

 formed across the cell dividing the protoplasm into two parts, 

 each containing one of the daughter nuclei. 



QUESTIONS 



1. Why may chlorophyll be considered the source of the food supply 

 of the world ? 



2. Discuss the transformations of energy in a green plant. 



3. If green plants are eaten by animals, what additional trans- 

 formations of energy may result ? 



4. Compare the oxidation of food in the plant cell with the oxidation 

 of coal in the school furnace, giving points of similarity and difference. 



5. Compare respiration in a green plant cell with photosynthesis, 

 considering materials used, products formed, products excreted, and 

 the purpose of the functions. 



6. Why may carbon be considered the real fuel of a green cell ? In 

 what form did it enter the cell? In what form did it ultimately 

 leave the cell ? Name all physiological functions involved in the use 

 of carbon. 



7. Trace the probable source of the carbon in coal. 



8. Discuss a balanced aquarium, stating the give and take of 

 materials between fish and green plants. 



9. In the figure on page 36 the possible intake and outgo of 

 materials in a green cell are shown. What are the actual interchanges 

 of materials ? 



SUPPLEMENTARY READING 



Coulter, Barnes, and Cowles, A Textbook of Botany (American Book Co.), 



Vol. I. 



Gager, C. S., General Botany (P. Blakiston's Son & Co.). 

 Holmes, S. J., General Biology (Harcourt, Brace & Co.), chap. vii. 



WH. FITZ. AD. BIO. 4 



