DEVELOPMENT OF THE SEEDLING 25 



are sometimes classified, root and shoot. All of these 

 organs may multiply and increase in size as the plant grows 

 older, and their mature structure will be studied in later 

 chapters, but some facts concerning them can best be 

 learned by watching their growth from the outset. 



33. Elongation of the Root. — We know that the roots 

 of seedlings grow pretty rapidly from the fact that each 

 day finds them reaching visibly farther down into the water 

 or other medium in which they are planted. A sprouted 

 "Windsor bean in a vertical thistle-tube will send its root 

 downward fast enough so that ten minutes' watching 

 through the microscope will suffice to show growth. To 

 find out just where the growth goes on requires a special 

 experiihent. 



EXPEUIMEXT IX 



In what Portions of the Root does its Increase in Length take place? 



— Sprout some peas on moist blotting paper in a loosely covered tum- 

 bler. "When the roots are one and a half inches or more long, mark 

 them along the whole length with little dots made with a bristle 

 dipped in water-proof India ink, or a fine inked thread stretched on 

 a little bow of whalebone or brass wire. 



Transfer the plants to moist blotting paper under a bell-glass or 

 an inverted battery jar and examine the roots at the end of twenty- 

 foui- hours to see along what portions their length has increased ; 

 continue observations on them for several days. 



34. Root-Hairs. — Barley, oats, wheat, red clover, or 

 buckwheat seeds soaked and then sprouted on moist blot- 

 ting paper ailord convenient material for studying root- 

 hairs. The seeds may be kept covered with a watch-glass 

 or a clock-glass while sprouting. After they have begun 

 to germinate well care must be taken not to have them 



