III. THE FUNCTIONS AND COMPOSITION OF LIVING 



THINGS 



Problem IV. An introduction to the nature and work of 

 living organisms. (Laboratory Manual, Prob. IV.) 



(a) A living plant. 

 (5) ,i living insect. 



-yA Living Plant and a Living Animal Compared. — A walk into the 

 fields or any vacant lot on a day in the early fall will give us first- 

 hand acquaintance with many common plants which, because of 

 their abihty to grow under sometimes 

 unfavorable conditions, are called weeds. 

 Such plants — the dandehon, butter and 

 eggs, the shepherd's purse — are particu- 

 larly well fitted by nature to produce 

 many of their kind, and by this means 

 drive out other plants which cannot do 

 this so well. On these or other plants 

 we find feeding several kinds of arumals, 

 usually insects. 



If we attempt to compare, for example, 

 a grasshopper with the plant on which it 

 feeds, we see several points of likeness and 

 difference at once. Both plant and insect 

 are made up of parts, each of which, as 

 the stem of the plant or the leg of the 

 insect, appears to be distinct, but which is 

 a part of the whole living plant or animal. 

 Each part of the living plant or animal 

 which has a separate work to do is called an organ. Thus plants 

 and animals are spoken of as living organisms. 



Functions of the Parts of a Plant. — We are all familiar with 

 the parts of a plant, — the root, stem, leaves, flowers, and fruit. 



26 



A Weed. Notice the un- 

 favorable habitat. Pho- 

 tograph by W. A. Bar- 

 bour. 



