LABORATORY STUDIES 9 
ete., as well as a few simple reagents such as alcohol, iodine- 
potassium-iodide solution, potash solution, etc. ‘The measure- 
ments used throughout this book are metric; 1 em. =0.394 in. 
1 mm.=about 1/25 inch, 1 micron (written ~)=0.001 mm. 
(i.e. about one-twenty-five-thousandth of an inch). 
(a) Make a thin longitudinal section of the tip of a large 
root of Indian corn or hyacinth or any other plant with stout 
roots, or of the growing point of a herbaceous stem, and 
mount in water and examine under the microscope. The 
small cells near the tip will be found to be full of protoplasm. 
The following tests should be made on different sections: (1) 
Add strong iodine solution; this turns the protoplasm brown 
or yellowish brown. (2) Test with a drop or two of Millon’s 
reagent (dissolve a small amount of mercury in an equal weight 
of strong nitric acid, and dilute with an equal amount of 
distilled water. Use fresh): the protoplasm is turned bright 
yellow. (3) Mount a section in strong sugar solution and 
after a few moments add a drop of fairly strong sulphuric 
acid: the protoplasm is stained red or pink. (4) Treat a 
section with nitric acid and then with strong potash: the yellow 
color of the protoplasm shows the so-called xanthoprotein 
reaction. 
(b) Repeat these tests with raw white of egg, which consists 
of proteins. Note that the results are the same. For the 
sulphuric-acid-sugar test it is more satisfactory to mix the egg 
white with a strong sugar solution in a test tube, rolling the 
latter so that the sides are moistened with the mixture. Now 
very carefully run a small drop of concentrated sulphuric acid 
down the side of the tube. This browns the solution where 
it comes in contact in most concentrated form but at the edge 
of its path and at its point of entrance into the mixture the 
red coloration is shown beautifully. 
(c) To study the motion of cytoplasm make a cross or 
longitudinal section of a stem (the upper, younger portion) of 
Petunia or tomato without injuring the hairs. Mount in 
water and examine a cell of a hair. The cytoplasm will 
usually be found to be streaming. Note that the streams seem 
frequently to center upon the nucleus. Note the effect upon 
the Jnotion of placing the slide on a piece of ice. Warm it up 
again to a temperature of about 30° to 35° C. and note the 
