62 BOTANY: PRINCIPLES AND PROBLEMS 



31. Botanists distinguish between physical drought and physiological 

 drought. In what does this difference consist? 



32. What is the chemical composition of the ash of three important 

 crop-plants? (Take figures from any reliable determination.) How does it 

 happen that the substances and their proportions are different in the 

 different crops? 



33. What is the difference between a nutritive and a balanced solution for 

 plant growth? 



34. What relation is there between the osmotic pressure of a substance and 

 the gas pressure exerted by this substance in its gaseous state? 



35. Give the derivation of the following terms and explain in what way 

 each is appropriate: 



Protoplasm Vacuole Osmosis 



Cytoplasm Plastid Imbibition 



Nucleus Diffusion Plasmolysis 



