310 BOTANY: PRINCIPLES AND PROBLEMS 



REFERENCE PROBLEMS 



117. Name some algae which are of economic importance. 



118. What is "diatomaceous earth" and how was it produced? 



119. Give an example of a change in some agricultural practice which has 

 come about since the existence and importance of bacteria have become 

 recognized. 



120. What is "Pasteurization" and how is it useful? 



121. Species of bacteria which look alike may often be distinguished 

 from one another by differences in their physiological activity. What 

 examples can you cite from the seed plants of the use of physiological 

 differences to distinguish two plant varieties which look very similar? 



122. What is the life history of the white pine blister rust and what is a 

 good means for combatting this fungus? 



123. What are fungus galls and how are they produced? 



124. What are "fairy rings" and how do you explain them? 



125. How are truffles gathered? 



126. What parasitic animals are there whose life history is somewhat 

 analogous to that of the rusts? 



127. Who first discovered that lichens are composed of algae and 

 fungi ? 



128. What lichens are of economic importance? 



129. Give the derivations of the following terms and explain why each is 

 appropriate : 



Heterocyst Pyrenoid Basidium 



Zoospore Plankton Perithecium 



Zygospore Trichogyne Hymenium 



Oospore Mycelium Sterigma 



Heterogamy Toxin Teleutospore 



Antheridium Conidium Uredospore 



Oogonium Aseus Aecidium 

 Soredium 



