THE TlfALLOPHYTA 307 



697. Which of the other algae do the red algae most resemble in their 

 reproductive structures? 



698. \\'liat makes us believe that the fungi have come from the algae 

 rather than the algae from the fungi? 



699. There are many more species of fungi than of algae. Explain. 



700. Which are larger plants, on the whole, the fungi ov the algae. 

 Why? 



701. Why do you think it is that most fungi inhabit the land and most 

 the water? 



702. Is wind or water the commoner agencj^ for the distribution of 

 the spores of the algae? of the fungi? 



703. AVhy are so many fungi edible, but so few algae? 



704. Why are fungi so much more important economically than algae? 



705. Through what steps do you think that the parasitic habit in 

 fungi may have arisen? 



706. Spores of a given species of parasitic fungus will generally 

 germinate and grow only on one or at most a few host plants. Is 

 there anything analogous to this "discriminating power" in any of the 

 other physiological activities of plants? 



707. Why are the fungous diseases of plants so much moi-e common in 

 the United States now than they were two hundred years ago? 



708. Why is a wcnuid much more lialjle to attack by fungi than is a 

 healthy area? 



709. Why are the fungous diseases usuall}' more prevalent in wet 

 seasons than in dry? 



710. Why is a spray of such a substance as copper sulphate effective 

 in preventing fungus attacks on plants? 



711. How do you explain the fact that a piece of moist bread shut 

 up in a box will almost always develop mold? 



712. Why do you think it is that the bacteria are the commonest 

 disease-producing parasites in animals, but that the higher fungi are the 

 most important causes of disease among plants? 



713. From an agricultural point of view, what various means can 

 you suggest for combatting the attacks of the fungous diseases of 

 crop plants? 



