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 
experiment. 
EXPERIMENT 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- 
four 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 afford 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 
