REPRODUCTION 203 



turn green and commence photosynthctic activity, soon supply- 

 ing an abundance of food which insures the rapid development of 

 the plant from the seedling stage to maturity, at which point the 

 cycle of reproduction is complete. 



QUESTIONS FOR THOUGHT AND DISCUSSION 



538. Is asexual reproduction commoner in animals or in plants? 

 Explain. 



539. Give an example of a plant which commonly reproduces itself 

 Asexually. 



540. What advantage is it to the potato to reproduce by tubers rather 

 than by seeds? What disadvantage is there in this process? 



541. What advantages, aside from the one mentioned in j'our text, 

 may sexual reproduction have over asexual multiplication? 



542. What connection do you think there has been between the 

 stationary habit so characteristic of plants and their reproduction by 

 means of flowers? 



543. The petals of a flower usuall.v drop off after seed is set but the 

 sepals commonly remain. Of what advantage are these two facts to 

 the plant? 



544. Pollen grains are often roughened. Explain. 



545. Can you suggest what makes the pollen grain germinate and why 

 it grows down the style directly to the ovule? 



546. Why is pollen generally spoiled if it is wet by the rain? 



547. What effect does the weather at apple-blossom time have ui)on 

 the size of the subsequent apple crop? 



548. Do you think that the earliest seed plants were pollinated by 

 wind or l)y insects? Why? 



549. What advantages and what disadvantages are there in wind- 

 pollination? 



550. Trees which are wind-j^ollinated usually flowor oarly in the 

 spring. Explain. 



551. The flowers of most coniferous trees are borne near the ends of 

 the branches, and the flowers of grasses are usually raised up on a tall 

 spike. Explain these facts. 



