82 REPRODUCTION 



as the pistillate trees, although they had no explanation for this 

 phenomenon of nature. 



Self-Pollination. However, the flowers of some plants are 

 very generally self-pollinated. Wheat belongs to this group or 

 class. 



Buds That Never Open. The buds of some flowers never 

 open, making cross pollination impossible. Such flowers are 

 called cleistogamous. Some species of violets produce incon- 

 spicuous cleistogamous buds under the leaf -mold, these buds pro- 

 ducing abundant seeds, while the showy* flowers of these species 

 are usually sterile. 



EXERCISES IN POLLINATION 



1. Carriers of Pollen. Observe flowers and note the insects which 

 visit them. Are the different species of flow<ers visited by the same species 

 of insects ? Do the insects exercise a choice in visiting flowers ? , 



2. Examine pollen of a number of flowers under the microscope. Make 

 drawings. 



3. Pollen Growth in Sugar Solution. Make a solution by boiling 

 one part of sugar in, ten of water. Put a spoonful into each of several 

 watch glasses. Mix the pollen of several flowers into them and keep cov- 

 ered. Examine a drop of the fluid with pollen under the miscroscope from 

 time to time and note the germination. 



QUESTIONS 



1. How* do you account for the rapid increase in numbers of willows 

 and similar plants along water courses ? 



2. Can other plants be produced in a similar manner ? 



3. How do we make) use of this power of reproduction in the grow- 

 ing plant? 



4. How are many grasses and other pests frequently propagated? 



5. Give a list of plants that grow from bulbs. 



6. Give a list of plants that grow from tubers. 



7. Give a list of plants that are seldom or never grown from seeds. 

 How are they grown? 



8. Do roots produce bud? Give some exceptions. 



9. Explain pollination. 



10. Explain fertilization. 



11. Explain cross pollination. 



12. Explain self-pollination. 



13. Explain cleistogamous seed production. 



