32 ROOTS 
scope. You will find some of their tips covered by a sort 
of hood-like sheath, called a root-cap. Remove some of 
the caps with your needles. Draw a root-tip in outline, 
showing the root-cap, and describe. Root-caps will be- 
more thoroly studied later. 
Complete exp. 1 by pulling up some of each of the 
different kinds of plants and studying their roots. To 
which class above mentioned do these roots belong? You 
will find two root systems, known respectively as tap and 
fibrous systems. What advantage has a tap root system 
over a fibrous system? Has a fibrous system any ad- 
vantage over a tap root system? Outside the laboratory 
study the roots of dandelion, clover, yellow-dock, grasses 
of various kinds, etc. No notes will be required on the 
study of roots outside the laboratory, but be prepared to 
answer questions concerning them. On the clover roots 
note small enlargements, tubercles. Mount one in water 
and crush it under the cover-glass. Note that it con- 
tains numerous very small bodies which are in motion. 
These bodies are bacteria. The instructor will discuss 
their importance. 
Exp. 20, Groups of Two: Select four pea or corn 
seedlings with straight radicles between I and 2 cm. long 
and put a row of dots of India ink 1 mm. apart on the 
radicles of two of them, beginning at the apex. On the 
radicles of the two others make heavy continuous lines 
from end to end. Fasten these seedlings to a support in 
a damp chamber, with the radicles pointing downward. 
Study the development of these roots for a day or two. 
Results; conclusions? 
Exp. 21, Class: Select a large sound carrot; bore a 
