LABORATORY STUDIES 9 



etc., 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 cm. = 0.394 in. 

 1 mm. = about 1/25 inch, 1 micron (written JJL)= 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. 



(6) 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 motion 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 



