16 A LABORATORY MANUAL OF BOTANY 
particles of sawdust or sand held by the roots? What hap- 
pens when the end of a root-hair grows against a solid body? 
Remove from the soil one of the sunflower plants and 
note the distribution of its root-hairs. Pull the roots bear- 
ing root-hairs through the hand in such a way that all the 
root-hairs will be injured. The drying which occurs while 
the examination is being made will injure at once some of 
the root-hairs. Repot the plant. 
Remove and repot another plant, taking care to keep the 
root-hairs moist and uninjured. Give both plants plenty 
of water. Note the plants after intervals of a few hours, 
and one and two days, and see if they wilt and regain their 
normal condition in the same way. Examine the first plant 
after a few days to see if it has developed new hair-roots. 
Have the notes contain a full comparison of the behavior 
of these two plants, the facts illustrated by their behavior, 
and some inferences from these facts. 
Cut off the stem of a good thrifty plant; over the stump 
slip a short closely fitting piece of rubber tubing, and into 
the tubing place a piece of glass tubing; with string and 
paraffin, or beeswax, make the joints water-tight. Keep 
the roots well watered. After interv-ls note whether water 
rises in the glass tube. If so, note the amount of rise at 
different intervals.+ 
The roots of plants serve at least two general purposes. 
They hold the plants in place and the root-hairs absorb 
water from the soil and help to force it up the stem into 
the leaves. Without the root-hairs plants which grow in 
the earth can not take up enough water to serve for their 
needs. The root-hairs are developed from surface cells of 
the smallest roots, are never at the root-tip or on old roots," 
and are very delicate, short-lived structures. 
1 Tf the classes are large, it may be advisable for the teacher and a 
few pupils to prepare these experiments, all observing and making 
drawings and notes on the preparations and the results, 
