THE PLANT KINGDOM 261 



(or its abbreviation) of the botanist who first used this name for 

 the species in question. Thus the full name of the Dog Rose is 

 Rosa canina L., which means that this particular name was 

 conferred on the plant by Linnaeus. Disputes still arise as to 

 just what certain species should be called, for different botanists 

 have sometimes given different names to the same plant. Such 

 questions must be settled by the adoption of universal rules 

 and practices, and it is to be hoped that through them the 

 nomenclature of plants may in time become perfectly uniform 

 throughout the world. 



With this introduction to the history, classification, and nomen- 

 clature of plants^ we shall proceed in the next four chapters to 

 describe briefly the main features of the four great divisions of 

 the vegetable kingdom. 



QUESTIONS FOR THOUGHT AND DISCUSSION 



639. Do you think that the first organisms to appear on the earth 

 were more nearly like plants or like animals? Why? 



640. It is generally agreed that the earliest plants lived in the water. 

 What evidence can you think of for this? 



641. Do you think that the earliest plants were motile or not? Why? 



642. What are the advantages and the disadvantages of a many- 

 celled as compared with a single-celled plant? 



643. What basis would you use to determine whether a group of cells 

 is a colony or a single plant? 



644. In what way is an animal individual a more distinct and definite 

 thing than a plant individual? 



645. Why is the increased size of the plant body, beyond a certain 

 point, necessarily followed by the beginning of differentiation? 



646. Why were the sexual cells the first ones to become differentiated 

 from the ordinary body cells of the plant? 



647. In general, is there a higher degree of differentiation in the body 

 of a water plant or of a land plant? Explain. 



648. State all the resemblances you can find Iwtweon a plant and a 

 civilized nation. 



649. What oilw.v advantages can you think of, aside from increased 

 vigor, which sexual reproduction might possess over asexual? 



