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 flowers 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 Grovi^th in Sugar Solution.— ^lake 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 w^e 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 buda? Give some exceptions. 



9. Explain pollination. 



10. Explain fertilization. 



11. Explain cross pollination. 



12. Explain self-pollination. 



13. Explain cleistogamous seed production. 



