ROOTS. a0 
weight of water. Grasses have been known to take in their 
weight of water in every twenty-four hours of warm, dry 
weather. This absorption takes place mainly through the 
reot-hairs, which the student has examined as they occur in 
the seedling plant, and which are found thickly clothing the 
younger and more rapidly growing parts of the roots of 
mature plants. Some idea of their abundance may be gath- 
ered from the fact that on a rootlet of corn grown in a damp 
atmosphere, and about j; inch in diameter, 480 root-hairs 
have been counted on each hundredth of an inch in length. 
The walls of the root-hairs are extremely thin, and they are 
free from any holes or pores which can be seen even by the 
highest power of the microscope, yet the water of the soil 
penetrates very rapidly to the interior of the root-hairs. 
The soil-water brings with it all the substances which it can 
dissolve from the earth about the plant; and the closeness 
with which the root-hairs cling to the particles of soil, as 
shown in Fig. 19, must cause the water which is absorbed 
-to contain more foreign matter than underground water in 
general does, particularly since the roots give off enough 
weak acid from their surface to corrode the surface of stones 
which they enfold or cover. 
51. Osmose.— The process by which two liquids separated by 
membranes pass through the latter and mingle is called osmose. 
52. Experiment 15.* Osmose in an Egg. — Cement to the smaller 
end of an egg a bit of glass tubing about six inches long and about ;'; 
inch inside diameter. Sealing wax or a mixture of equal parts of bees- 
wax and rosin melted together will serve for a cement. 
Chip away part of the shell from the larger end of the egg, place it in 
a wide-mouthed bottle or a small beaker full of water, as shown in 
Fig. 21, then very cautiously pierce a hole through the upper end of the 
egg-shell by pushing a knitting-needle down through the glass tube. 
Watch the apparatus for some hours and note the gradual rise of the 
contents of the egg in the tube.} 
1 Testing the contents of the beaker with nitrate of silver solution will then show 
the presence of a little common salt in the water. 
