III. PROTOPLASM AND THE CELL 



A Living Plant. — If we walk out any afternoon in the fall of 

 the year, we notice the many forms of plant life that fill the waste 

 places along the waysides 

 and make their way into 

 the cultivated gardens 

 and fields, driving out 

 the rightful inhabitants. 

 We call such plants 

 weeds. Let us study 

 some common weed such 

 as the yellow-blossomed 

 butter and eggs or the 

 ubiquitous shepherd's 

 purse, with the intention 

 of finding out how such 

 plants are so well fitted 

 to live. If we think of the 

 plant as a mass of living 

 matter, we at once are 

 struck with the evident 

 fact that the living ma- 

 terial has taken on very 

 different forms in dif- 

 ferent parts of the plant. ^ 

 The root below the sur- 

 face of the ground dif- 

 fers considerably in form 

 from the stem, which in turn differs in structure from the leaves. 



^ The living matter of the plants is covered by dead organic matter formed by the 

 activity of the live part. Thus the soft living mass within may be molded into 

 various shapes, as stem, root, or leaves, with the help of the strong and rigid dead 

 parts of the plant. 



23 



Shepherd's purse; F^ flowers; F, fruits; 5, stem; 

 L, leaves; R, roots. 



