158 SOUTH AFRICAN BOTANY 
takes place the following experiments may be per- 
formed. 
Experiment 29.—Obtain some germinating seeds 
with radicles about half an inch long. Mealies, 
Beans, Peas, Sunflowers will all do for this experi- 
ment. Get a ruler graduated in millimetres, some 
indian ink, and a fine pen. Now mark all the 
radicles with fine lines a millimetre apart, beginning 
at the tip. Then place the seeds on damp blotting- 
paper or damp sawdust and leave for twenty-four 
hours. Then notice the position of the marks. If 
the experiment is done on a cold day it may be neces- 
sary to leave the seedlings for two days. Sketch the 
seeds (w) as they were, (b) as they are now. The reason 
that the part behind the tip increases in length, and not 
the tip itself 1s that the cells at the tip behind the root- 
cap are all meristematic, i.e. they are rapidly dividing 
and forming new cells, whereas those a little farther 
back are expanding to their full size. Hence it is in this 
region that the greatest increase in length is noticeable, 
though the actual growth takes place just behind the 
root-cap. 
Experiment 30.—To observe the elongation of the 
stem some young seeds should be taken in which the 
plumule is just out. A Broad Bean or Pea seedling is 
best for this, as in the mealie the actual growing point 
of the stem is wrapped around by the sheathing leaves, 
and hence cannot be marked. Mark the plumule in 
the same way as the radicle, and proceed as before. 
Opening buds can also be used for this experiment, 
those of the Oak are suitable; the short internodes 
