CHAPTER XXXI 

 REPRODUCTION IN PLANTS AND ANIMALS 



370. Questions for Discussion. 1. If a yeast plant can itself become 

 full grown and produce one new yeast plant in twenty minutes, and 

 this rate continues for twenty-four hours, how many yeast plants will 

 be produced from one plant in that time? 2. Does the rate of repro- 

 duction of yeast plants have anything to do with the rate at which 

 fermentation by yeast occurs? 3. How long does it take for a forest 

 tree to reproduce itself by a tree as large as the old tree? 4. If pos- 

 sible, secure frog's eggs or toad's eggs and allow them to develop in 

 a dish of shallow water. Trace day by day the stages in development. 

 5. In what respects is reproduction by eggs similar or dissimilar in 

 birds and flowering plants ? 6. What common farm, garden, and house 

 practices with plants depend on vegetative reproduction ? 7. From your 

 state agricultural experiment station secure a bulletin on propagation 

 of plants by cuttings and by grafting, and if possible follow the direc- 

 tions given in some home experiments. 8. Are you the more sure of 

 securing the desired kind of cultivated fruits when growing them from 

 cuttings or from seeds? Why? 



371. The meaning of reproduction. Thus far our discussions 

 of plants and animals have dealt with problems in nutrition. 

 In many ways those problems are of the greatest importance. 

 But no matter how well nourished a plant or animal may be, 

 its kind will cease to exist on the earth unless there are means 

 by which new and younger individuals can be produced. 

 The process by which younger individuals are produced is 

 known as reproduction (which means "producing again"). 



In the bodies of plants and animals the cells divide, each 

 cell forming two new cells from one old one. This is repro- 

 duction of cells. In most plants and animals increase in 

 number of cells and the enlargement that results is called 



